Assimilatory sulfate reduction to sulfide (APS and PAPS routes)

Assimilatory sulfate reduction supplies sulfide for sulfur-containing metabolites in characterized bacterial, fungal and plant systems. ATP sulfurylase first forms APS. Activated sulfate is then reduced either directly by an APS reductase or after APS kinase forms PAPS. The plant APS reductase exemplar uses glutathione through a fused redox domain; bacterial APS and fungal PAPS reductases have distinct external redox-partner requirements. Siroheme/iron-sulfur sulfite reductases complete the six-electron reduction, using characterized NADPH-linked complexes or ferredoxin-linked enzymes; the immediate carrier in the Pseudomonas Fpr-linked system remains unresolved. Sulfate import, cofactor biosynthesis, reductant regeneration and downstream sulfide incorporation are boundary processes.

MODULE:aps_dependent_assimilatory_sulfate_reductionCOMPLETECONCRETEMetabolic Pathwaymodules/aps_dependent_assimilatory_sulfate_reduction.yaml
sulfate assimilationGO:0000103
GO:0000103
sulfate assimilation
GO:0000103 provides the biological-process context.
RHEA:18133
sulfate adenylyltransferase reaction
RHEA:18133 defines ATP-dependent formation of APS from sulfate.
RHEA:21976
adenylyl-sulfate reductase reaction
RHEA:21976 defines the reversible thioredoxin-dependent APS/sulfite reaction catalyzed physiologically toward sulfite during assimilation.
GO:0004020
adenylylsulfate kinase activity
APS kinase step of the PAPS route.
GO:0004604
phosphoadenylyl-sulfate reductase (thioredoxin) activity
PAPS reductase step of the PAPS route.
GO:0050311
sulfite reductase (ferredoxin) activity
GO:0050311 captures a ferredoxin-fed sulfite-reductase implementation; the immediate donor must still be established in each concrete system.
PANTHER:PTHR32439
ferredoxin sulfite/nitrite reductase family
This broad siroheme-reductase family includes bacterial sulfite and nitrite reductases; family membership alone does not identify substrate specificity or the physiological electron carrier.
GO:0004783
sulfite reductase (NADPH) activity
GO:0004783 captures the NADPH-dependent implementations (enterobacterial CysJ/CysI and fungal Met10/Met5).
YeastPathways:SO4ASSIM-PWY
assimilatory sulfate reduction I (S. cerevisiae, SGD YeastPathways)
Four reactions with MET3 (ATP sulfurylase), MET14 (APS kinase), MET16 (PAPS reductase) and MET10 + MET5 (NADPH sulfite reductase). All assignments were retained; the thioredoxins (TRX1, TRX2) that supply reducing equivalents to MET16 are absent from the gene list and were added as the PAPS-reductase electron-donor role.
YeastPathways:PWY-781
sulfate assimilation pathway (S. cerevisiae, SGD YeastPathways)
Same four reactions and catalysts as SO4ASSIM-PWY, with a comment covering sulfate uptake (SUL1, SUL2, outside this module), the activation-reduction sequence and Met4-dependent regulation.
YeastPathways:PWY-5340
sulfate activation (for sulfonation) (S. cerevisiae, SGD YeastPathways)
MET3 and MET14 producing PAPS; this is the activation prefix of the PAPS route of this module and is not modelled separately.
PMID:9409150
Metabolism of sulfur amino acids in Saccharomyces cerevisiae.
Review of the S. cerevisiae sulfate assimilation pathway cited by YeastPathways.
PMID:197388
Methionine biosynthesis in Saccharomyces cerevisiae. II. Gene-enzyme relationships in the sulfate assimilation pathway.
Classical gene-enzyme mapping of the yeast sulfate assimilation pathway, the basis of the MET3, MET14 and MET16 assignments in GOA.
PMID:11157739
Crystal structure of ATP sulfurylase from Saccharomyces cerevisiae, a key enzyme in sulfate activation.
The yeast MET3 structure is homohexameric. Proteobacterial sulfurylases instead contain interacting CysD and CysN subunits, whose higher-order assembly is species- and experiment-specific.
The enzyme consists of six identical subunits arranged in two stacked rings in a D:3 symmetric assembly.
PMID:18388974
Cloning of the ATP sulphurylase gene of Schizosaccharomyces pombe by functional complementation.
S. pombe sua1 encodes ATP sulfurylase and complements an S. cerevisiae met3 mutation.
The cloned sua1 gene also complemented the met3 (ATP sulphurylase deficient) mutation in Saccharomyces cerevisiae.
PMID:1654509
Cloning, nucleotide sequence, and regulation of MET14, the gene encoding the APS kinase of Saccharomyces cerevisiae.
MET14 encodes S. cerevisiae APS kinase.
The MET14 gene of Saccharomyces cerevisiae, encoding APS kinase (ATP:adenylylsulfate-3'-phosphotransferase, EC 2.7.1.25), has been cloned.
PMID:2203779
Gene-enzyme relationship in the sulfate assimilation pathway of Saccharomyces cerevisiae. Study of the 3'-phosphoadenylylsulfate reductase structural gene.
MET16 is the structural gene for yeast PAPS reductase, which is similar to E. coli CysH.
we show that MET16 is the structural gene for PAPS reductase and that the yeast and the Escherichia coli enzymes display significant similarities.
PMID:3060034
Yeast PAPS reductase: properties and requirements of the purified enzyme.
Purified yeast PAPS reductase requires reduced thioredoxin as cosubstrate.
Reduced thioredoxin is required as cosubstrate.
PMID:2026619
Thioredoxin deficiency in yeast prolongs S phase and shortens the G1 interval of the cell cycle.
The tested yeast trx1 trx2 double deletion is methionine auxotrophic. Later low-ROS experiments (PMID:10844700) limit the claim of universal thioredoxin requirement.
Surprisingly, the loss of both thioredoxins also leads to methionine auxotrophy. Thus yeast glutaredoxin is unable to substitute for thioredoxin in sulfate assimilation.
PMID:10613872
Identification of a new class of 5'-adenylylsulfate (APS) reductases from sulfate-assimilating bacteria.
Pseudomonas aeruginosa CysH is an APS reductase that bypasses PAPS, distinct from the E. coli PAPS reductase; this separates the two routes of the module.
Purified P. aeruginosa CysH expressed as a His-tagged recombinant protein is able to reduce APS, but not PAPS.
PMID:6751400
Studies on yeast sulfite reductase. IV. Structure and steady-state kinetics.
Yeast NADPH-sulfite reductase is an alpha2beta2 hemoflavoprotein.
The enzyme consists of two types of subunit, alpha and beta, having molecular weights of 116,000 and 167,000, respectively. The subunit structure is suggested to be alpha 2 beta 2.
PMID:7928966
Two divergent MET10 genes, one from Saccharomyces cerevisiae and one from Saccharomyces carlsbergensis, encode the alpha subunit of sulfite reductase and specify potential binding sites for FAD and NADPH.
MET10 encodes the flavoprotein alpha subunit, related to E. coli CysJ but lacking obvious FMN-binding motifs.
suggests that the yeast assimilatory sulfite reductase is a distinct type of sulfite reductase.
PMID:1479340
Physiological analysis of mutants of Saccharomyces cerevisiae impaired in sulphate assimilation.
MET5 and MET10 (subunits) and MET1, MET8 (siroheme synthesis) are needed for active sulfite reductase.
the products of at least five genes are needed for the synthesis of an enzymically active sulphite reductase. These genes are MET1, MET5, MET8, MET10 and MET20.
PMID:16387658
Molecular basis for G protein control of the prokaryotic ATP sulfurylase.
Biochemistry and structure establish the proteobacterial CysD/CysN complex and energetic coupling of CysN GTP turnover to APS formation.
PMID:23794620
Role for ferredoxin:NAD(P)H oxidoreductase (FprA) in sulfate assimilation and siderophore biosynthesis in Pseudomonads.
Pseudomonas genetics supports an FprA-linked sulfite-reduction system distinct from E. coli CysJI, without identifying the immediate electron carrier to CysI.
PMID:9653199
Purified Arabidopsis APR1 and separated-domain experiments establish glutathione-fed plant APS reduction.
PMID:30825314
Plant structural-biology review supplies comparative architecture and points to primary studies.
PMID:17644602
Purified M. tuberculosis SirA chemistry and M. smegmatis deletion/rescue distinguish biochemical target from native genetic host.
15Nodes
5Parts
3Variant Sets
9Variants
12Annotons
5Connections

Derived QC

Recommended-field compliance

100.0% recommended fields populated

All recommended fields populated.

Module deep research

✓ present

  • aps_dependent_assimilatory_sulfate_reduction-deep-research-openscientist.md (openscientist)

Leaf nodes lacking representative members

✓ every leaf node grounds to a representative protein.

Template conformance

✓ every declared conforms_to bundle matches its template motif.

Reaction chaining (advisory)

✓ every PRECEDES step chains, or its break is acknowledged via chaining_status.

  • sulfate_activation_step → aps_reduction_step [NOT_CHECKED]
  • aps_reduction_step → sulfite_reduction_step [NOT_CHECKED]

Function consistency and core coverage

23 gene-function check(s) reflected in core functions · 0 conflict(s) · 11 evidence or coverage gap(s) (45 comparison(s))

Retained noncore functions are reported separately; they do not require promotion to core functions. Support from representative genes does not establish conservation across the whole family. Missing reviews or identifiers leave a claim unverified.

AnnotonParticipantFunctionAssessment
cysdn_atp_sulfurylase PROTEIN_COMPLEX
Gene 		sulfate adenylyltransferase (ATP) activity
GO:0004781 		Participant Unchecked
No direct UniProt participant to compare. Abstract selectors and complex-wide activities cannot be inferred from donor or subunit gene reviews.
cysdn_atp_sulfurylase/cysd_catalytic_subunit cysD (Pseudomonas putida KT2440)
UniProtKB:Q88NA9
Family Representative 		sulfate adenylyltransferase (ATP) activity
GO:0004781 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
cysdn_atp_sulfurylase/cysd_catalytic_subunit cysD (Escherichia coli K-12)
UniProtKB:P21156
Family Representative 		sulfate adenylyltransferase (ATP) activity
GO:0004781 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
cysdn_atp_sulfurylase/cysn_regulatory_gtpase_subunit cysNC (Pseudomonas putida KT2440)
UniProtKB:Q88NA8
Family Representative 		GTPase activity
GO:0003924 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
cysdn_atp_sulfurylase/cysn_regulatory_gtpase_subunit cysN (Escherichia coli K-12)
UniProtKB:P23845
Family Representative 		GTPase activity
GO:0003924 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
met3_type_atp_sulfurylase MET3 (Saccharomyces cerevisiae)
UniProtKB:P08536
Family Representative 		sulfate adenylyltransferase (ATP) activity
GO:0004781 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
met3_type_atp_sulfurylase sua1 (Schizosaccharomyces pombe)
UniProtKB:P78937
Family Representative 		sulfate adenylyltransferase (ATP) activity
GO:0004781 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
met3_type_atp_sulfurylase APS1 (Arabidopsis thaliana)
UniProtKB:Q9LIK9
Family Representative 		sulfate adenylyltransferase (ATP) activity
GO:0004781 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
cysH_aps_reductase cysH (Pseudomonas putida KT2440)
UniProtKB:Q88KG2
Family Representative 		adenylyl-sulfate reductase (thioredoxin) activity
GO:0043866 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
cysH_aps_reductase cysH (Pseudomonas aeruginosa PAO1)
UniProtKB:O05927
Family Representative 		adenylyl-sulfate reductase (thioredoxin) activity
GO:0043866 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
apr1_glutathione_aps_reductase APR1 (Arabidopsis thaliana)
UniProtKB:P92979
Family Representative 		adenylyl-sulfate reductase (glutathione) activity
GO:0033741 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
aps_kinase_activity MET14 (Saccharomyces cerevisiae)
UniProtKB:Q02196
Family Representative 		adenylylsulfate kinase activity
GO:0004020 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
aps_kinase_activity met14 (Schizosaccharomyces pombe)
UniProtKB:Q9P7G9
Family Representative 		adenylylsulfate kinase activity
GO:0004020 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
aps_kinase_activity CysC (Escherichia coli K-12)
UniProtKB:P0A6J1
Family Representative 		adenylylsulfate kinase activity
GO:0004020 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
paps_reductase_activity MET16 (Saccharomyces cerevisiae)
UniProtKB:P18408
Family Representative 		phosphoadenylyl-sulfate reductase (thioredoxin) activity
GO:0004604 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
paps_reductase_activity met16 (Schizosaccharomyces pombe)
UniProtKB:Q10270
Family Representative 		phosphoadenylyl-sulfate reductase (thioredoxin) activity
GO:0004604 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
paps_reductase_activity CysH (Escherichia coli K-12)
UniProtKB:P17854
Family Representative 		phosphoadenylyl-sulfate reductase (thioredoxin) activity
GO:0004604 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
thioredoxin_electron_donor TRX1 (Saccharomyces cerevisiae)
UniProtKB:P22217
Family Representative 		protein-disulfide reductase activity
GO:0015035 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
thioredoxin_electron_donor TRX2 (Saccharomyces cerevisiae)
UniProtKB:P22803
Family Representative 		protein-disulfide reductase activity
GO:0015035 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
thioredoxin_electron_donor trx1 (Schizosaccharomyces pombe)
UniProtKB:O14463
Family Representative 		protein-disulfide reductase activity
GO:0015035 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
pseudomonas_cysi_activity cysI (Pseudomonas putida KT2440)
UniProtKB:Q88KB9
Family Representative 		sulfite reduction with unresolved physiological electron donor
GO:0016667 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
fpr_electron_supply fpr-I (Pseudomonas putida KT2440)
UniProtKB:Q88MD5
Family Representative 		ferredoxin-NADP+ reductase activity
GO:0004324 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
ferredoxin_sulfite_reductase sir (Mycobacterium tuberculosis H37Rv)
UniProtKB:P9WJ03
Family Representative 		sulfite reductase (ferredoxin) activity
GO:0050311 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
ferredoxin_sulfite_reductase SIR (Arabidopsis thaliana)
UniProtKB:Q9LZ66
Family Representative 		sulfite reductase (ferredoxin) activity
GO:0050311 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
cysji_nadph_sulfite_reductase PROTEIN_COMPLEX
Gene 		sulfite reductase (NADPH) activity
GO:0004783 		Participant Unchecked
No direct UniProt participant to compare. Abstract selectors and complex-wide activities cannot be inferred from donor or subunit gene reviews.
cysji_nadph_sulfite_reductase/cysi_nadph_hemoprotein_subunit cysI (Escherichia coli K-12)
UniProtKB:P17846
Family Representative 		contribution to sulfite reductase (NADPH) activity
GO:0004783 		Contributes In Complex
The review records contribution to this activity, matching the subunit's role as an active unit of the modelled complex.
met10_met5_nadph_sulfite_reductase PROTEIN_COMPLEX
Gene 		sulfite reductase (NADPH) activity
GO:0004783 		Participant Unchecked
No direct UniProt participant to compare. Abstract selectors and complex-wide activities cannot be inferred from donor or subunit gene reviews.
met10_met5_nadph_sulfite_reductase/met5_hemoprotein_subunit MET5 (Saccharomyces cerevisiae)
UniProtKB:P47169
Family Representative 		contribution to sulfite reductase (NADPH) activity
GO:0004783 		Contributes In Complex
The review records contribution to this activity, matching the subunit's role as an active unit of the modelled complex.
met10_met5_nadph_sulfite_reductase/met5_hemoprotein_subunit sir1 (Schizosaccharomyces pombe)
UniProtKB:Q1K9C2
Family Representative 		contribution to sulfite reductase (NADPH) activity
GO:0004783 		Contributes In Complex
The review records contribution to this activity, matching the subunit's role as an active unit of the modelled complex.
cysd_catalytic_subunit CysD sulfate adenylyltransferase subunit 2 family
PANTHER:PTHR43196:SF1
Family 		sulfate adenylyltransferase (ATP) activity
GO:0004781 		Family Supported
Family review supports GO:0004781 for PANTHER:PTHR43196:SF1. Safe for SF1 (CysD and NodP), as the catalytic subunit of the CysD-CysN complex; the complete activity requires CysN. Not supported for the uncharacterized SF2 proteins.
cysn_regulatory_gtpase_subunit CysN sulfate adenylyltransferase regulatory subunits
NCBIfam:TIGR02034
Family 		GTPase activity
GO:0003924 		Family Review Missing
No supported structured family review is available for NCBIfam:TIGR02034.
met3_type_atp_sulfurylase Sat/Met3-type sulfate adenylyltransferases
PANTHER:PTHR42700
Family 		sulfate adenylyltransferase (ATP) activity
GO:0004781 		Family Function Unreviewed
Family review leaves GO:0004781 UNRESOLVED. Not family-wide and not cleanly subfamily-scoped. It holds for every member that carries the ATP-sulfurylase (PF01747) domain: the fungal MET3-type enzymes (MET3, sua1, Penicillium met3) and the bifunctional bacterial fusions. It does not hold for the short CysC-only members, which sit in the same subfamilies (SF1 and SF3). Applicability is therefore decided by domain architecture, which the subfamily axis does not capture and for which no residue rule is defined here. The APS-dependent sulfate reduction module correctly uses a GO:0004781 required_function filter on its PTHR42700 selector; without that filter the selector would also pick up monofunctional APS kinases.
met3_type_atp_sulfurylase Sat/Met3-type sulfate adenylyltransferases
PANTHER:PTHR11055:SF46
Family 		sulfate adenylyltransferase (ATP) activity
GO:0004781 		Family Supported
Family review supports GO:0004781 for PANTHER:PTHR11055:SF46. Holds for members with the ATP sulfurylase domain: PAPSS1 (SF17), PAPSS2 (SF16) and the Arabidopsis plastid ATP sulfurylases (SF46, SF37, SF77, SF39). Not safe for the monofunctional APS kinases (MET14, met14, CysC, APK1-4). SF1 is excluded although its C. elegans member pps-1 is bifunctional, because most SF1 members are APS kinase only. No PAINT node asserts this term in the family. The PAPS sulfate activation module uses the family-level PTHR11055 selector for its ATP sulfurylase annoton without a required_function filter; that is safe for its human PAPSS representatives but would capture monofunctional APS kinases if applied across the family.
cysH_aps_reductase CysH APS reductases
NCBIfam:TIGR02055
Family 		adenylyl-sulfate reductase (thioredoxin) activity
GO:0043866 		Family Review Missing
No supported structured family review is available for NCBIfam:TIGR02055.
apr1_glutathione_aps_reductase plant APR1-type APS reductases with fused redox domain
PANTHER:PTHR46482:SF9
Family 		adenylyl-sulfate reductase (glutathione) activity
GO:0033741 		Family Function Unreviewed
Family review leaves GO:0033741 UNRESOLVED. Holds for the plant APRs, which have the C-terminal glutaredoxin-like domain (APR1 in SF9, APR2 in SF3, APR3 in SF14), but not for the bacterial CysH members that share SF9 with APR1 and lack that domain. Applicability follows domain architecture, not subfamily; no residue site is formalised.
aps_kinase_activity APS kinase / PAPS synthase family
PANTHER:PTHR11055:SF1
Family 		adenylylsulfate kinase activity
GO:0004020 		Family Supported
Family review supports GO:0004020 for PANTHER:PTHR11055:SF1. Safe for the monofunctional APS kinase subfamilies and the bifunctional PAPS synthases. Not safe for the Arabidopsis plastid ATP sulfurylases (SF46, SF37, SF77, SF39), which lack the APS kinase domain. The APS-dependent sulfate reduction module uses PTHR11055 with a GO:0004020 required_function and MET14/met14/CysC representatives, which is consistent; the family-level selector alone would also capture the plant ATP sulfurylases.
aps_kinase_activity APS kinase / PAPS synthase family
PANTHER:PTHR11055:SF63
Family 		adenylylsulfate kinase activity
GO:0004020 		Family Supported
Family review supports GO:0004020 for PANTHER:PTHR11055:SF63. Safe for the monofunctional APS kinase subfamilies and the bifunctional PAPS synthases. Not safe for the Arabidopsis plastid ATP sulfurylases (SF46, SF37, SF77, SF39), which lack the APS kinase domain. The APS-dependent sulfate reduction module uses PTHR11055 with a GO:0004020 required_function and MET14/met14/CysC representatives, which is consistent; the family-level selector alone would also capture the plant ATP sulfurylases.
paps_reductase_activity PAPS reductases
PANTHER:PTHR46509:SF1
Family 		phosphoadenylyl-sulfate reductase (thioredoxin) activity
GO:0004604 		Family Function Unreviewed
Family review leaves GO:0004604 UNRESOLVED. Safe for the PAPS reductases (fungal MET16/met16, A. nidulans sA, enterobacterial CysH), which lack the Fe-S cysteine motif. Not established for the bacterial APS reductases that share SF1 (M. tuberculosis CysH is an APS reductase; B. subtilis CysH reduces both). The distinguishing feature is the presence or absence of the -CC-X~80-CXXC- motif rather than subfamily membership; no residue site is formalised here because motif positions were not checked in each sequence. The APS-dependent sulfate reduction module uses SF1 with a GO:0004604 required_function and fungal plus E. coli representatives, which is consistent; the SF1 selector alone would also capture APS reductases.
thioredoxin_electron_donor cytosolic thioredoxins
Family 		protein-disulfide reductase activity
GO:0015035 		Family Id Missing
The family has no identifier linking it to a curated family review.
pseudomonas_cysi_activity ferredoxin sulfite/nitrite reductase family
PANTHER:PTHR32439
Family 		sulfite reduction with unresolved physiological electron donor
GO:0016667 		Family Function Unreviewed
Family review leaves GO:0050311 UNRESOLVED. Holds for the mycobacterial SirA enzymes in SF0, which reduce sulfite and not nitrite, but not for the plant and cyanobacterial nitrite reductases that share SF0. For the SF9 assimilatory CysI proteins of pseudomonads the sulfite chemistry is supported but the physiological electron donor is unresolved, so the ferredoxin-specific term is not asserted (see the P. putida cysI review). Not applicable to CobG or DsrA. Substrate and donor are member properties, not subfamily properties.
fpr_electron_supply bacterial type-1 ferredoxin--NADP reductases
PANTHER:PTHR47878:SF1
Family 		ferredoxin-NADP+ reductase activity
GO:0004324 		Family Supported
Family review supports GO:0004324 FAMILY_WIDE. NADPH-dependent reduction of ferredoxin is measured for E. coli, Azotobacter, Rhodobacter and P. aeruginosa Fpr and for P. putida Fpr-I (which reduces both Fd and Fld, more efficiently Fld). Several members prefer flavodoxin, but the ferredoxin activity is not absent, so the term is safe family-wide.
ferredoxin_sulfite_reductase siroheme sulfite-reductase families with ferredoxin-linked implementations
PANTHER:PTHR32439
Family 		sulfite reductase (ferredoxin) activity
GO:0050311 		Family Function Unreviewed
Family review leaves GO:0050311 UNRESOLVED. Holds for the mycobacterial SirA enzymes in SF0, which reduce sulfite and not nitrite, but not for the plant and cyanobacterial nitrite reductases that share SF0. For the SF9 assimilatory CysI proteins of pseudomonads the sulfite chemistry is supported but the physiological electron donor is unresolved, so the ferredoxin-specific term is not asserted (see the P. putida cysI review). Not applicable to CobG or DsrA. Substrate and donor are member properties, not subfamily properties.
ferredoxin_sulfite_reductase siroheme sulfite-reductase families with ferredoxin-linked implementations
PANTHER:PTHR11493:SF47
Family 		sulfite reductase (ferredoxin) activity
GO:0050311 		Family Function Unreviewed
Family review leaves GO:0050311 UNRESOLVED. Plant plastid sulfite reductases only (PAINT node PTN008519198, Streptophyta). They share SF47 with the NADPH enzymes, so no subfamily is safe; must not be applied to MET5, sir1 or CysI.
cysi_nadph_hemoprotein_subunit NADPH-dependent CysI hemoproteins
PANTHER:PTHR11493:SF47
Family 		contribution to sulfite reductase (NADPH) activity
GO:0004783 		Family Function Unreviewed
Family review leaves GO:0004783 UNRESOLVED. Holds (as contributes_to, in the complex) for the fungal MET5/sir1 and enterobacterial CysI hemoproteins, but not for the plant ferredoxin-dependent enzymes, which share SF47. The donor is decided by the partner architecture, not by the subfamily, so the term must be scoped by PAINT node (PTN001285008 for fungi) or by member. The aps module correctly attaches GO:0004783 to the MET10/MET5 and CysJ/CysI complexes rather than to SF47 alone; an SF47 selector without a complex or required_function constraint would also pick up plant ferredoxin-sulfite reductases.
met5_hemoprotein_subunit NADPH sulfite reductase hemoproteins
PANTHER:PTHR11493:SF47
Family 		contribution to sulfite reductase (NADPH) activity
GO:0004783 		Family Function Unreviewed
Family review leaves GO:0004783 UNRESOLVED. Holds (as contributes_to, in the complex) for the fungal MET5/sir1 and enterobacterial CysI hemoproteins, but not for the plant ferredoxin-dependent enzymes, which share SF47. The donor is decided by the partner architecture, not by the subfamily, so the term must be scoped by PAINT node (PTN001285008 for fungi) or by member. The aps module correctly attaches GO:0004783 to the MET10/MET5 and CysJ/CysI complexes rather than to SF47 alone; an SF47 selector without a complex or required_function constraint would also pick up plant ferredoxin-sulfite reductases.

Gene-review completeness (29/29 grounded genes reviewed)

29 complete review(s) · 9 with deep research · 0 missing review · 20 reviewed but lacking deep research

Gene Review Complete Deep research
APR1 P92979 ✓ ✓ ✗
APS1 Q9LIK9 ✓ ✓ ✗
cysC P0A6J1 ✓ ✓ ✗
cysD P21156 ✓ ✓ ✗
cysD Q88NA9 ✓ ✓ ✗
cysH O05927 ✓ ✓ ✗
cysH P17854 ✓ ✓ ✗
cysH Q88KG2 ✓ ✓ ✓
cysI P17846 ✓ ✓ ✗
cysI Q88KB9 ✓ ✓ ✓
cysJ P38038 ✓ ✓ ✗
cysN P23845 ✓ ✓ ✗
cysNC Q88NA8 ✓ ✓ ✗
fpr-I Q88MD5 ✓ ✓ ✗
MET10 P39692 ✓ ✓ ✓
met10 Q09878 ✓ ✓ ✗
MET14 Q02196 ✓ ✓ ✓
met14 Q9P7G9 ✓ ✓ ✗
MET16 P18408 ✓ ✓ ✓
met16 Q10270 ✓ ✓ ✗
MET3 P08536 ✓ ✓ ✓
MET5 P47169 ✓ ✓ ✓
sir P9WJ03 ✓ ✓ ✗
SIR Q9LZ66 ✓ ✓ ✗
sir1 Q1K9C2 ✓ ✓ ✗
sua1 P78937 ✓ ✓ ✗
trx1 O14463 ✓ ✓ ✗
TRX1 P22217 ✓ ✓ ✓
TRX2 P22803 ✓ ✓ ✓

Details

Context
BacteriaNCBITaxon:2 FungiNCBITaxon:4751 ViridiplantaeNCBITaxon:33090
Assimilatory sulfate reduction (APS and PAPS routes)Metabolic Pathwayaps_dependent_assimilatory_sulfate_reduction
sulfate assimilationGO:0000103
Context
BacteriaNCBITaxon:2 FungiNCBITaxon:4751 ViridiplantaeNCBITaxon:33090

Union of supported assimilatory implementations, not a claim that every member of these clades possesses the complete pathway. Individual activities, substrates and electron donors require target-specific evidence; dissimilatory sulfate reduction and animal PAPS synthesis are outside scope. This template distinguishes sulfate activation, substrate-specific APS/PAPS reduction and terminal sulfite reduction. Fungal GO-CAM anchors remain; enzyme families are constrained by functional evidence. Plant APR1 is glutathione-dependent with a fused redox domain, and plant APS kinase used for sulfation is not evidence for a PAPS-reductive pathway. The native carrier in Pseudomonas Fpr-linked reduction is unresolved. The old P9WJ02 CDC1551 exemplar was corrected to characterized H37Rv P9WJ03. No module-wide compartment is asserted: fungal cytosol and plant plastids are distinct. Siroheme biosynthesis, redox regeneration, PAP recycling and downstream sulfide incorporation remain separate. Existing OpenScientist reports are discovery material, not primary evidence. Every PANTHER family of the 29 grounded members has a family review; CysN and the bacterial APS reductases are selected by NCBIfam TIGR02034 and TIGR02055 because their PANTHER families (PTHR23115, PTHR46482:SF9) also hold translation factors or plant APRs. The remaining FAMILY_FUNCTION_UNREVIEWED conformance warnings are deliberate: those family reviews leave the activity UNRESOLVED because it is decided by domain architecture, substrate or partner rather than by subfamily, and the module constrains each selector with named representatives and a required_function. Detailed source limits and provider failures are recorded in module notes.

Connections

ATP sulfurylase supplies APS to APS reductase or APS kinase.
PMID:197388
Yeast gene-enzyme relationships ground the PAPS-dependent activation and reduction sequence.
PMID:10613872
P. aeruginosa CysH supports the alternative direct APS-to-sulfite route.
PMID:9653199
Plant APS reductase supplies the direct glutathione-fed reduction step.
PMID:20424176
Plant sulfur-flux perturbation and complementation ground the downstream sulfite-reduction step.
APS or PAPS reduction supplies sulfite to the terminal sulfite-reduction system.
PMID:197388
Yeast gene-enzyme relationships ground the PAPS-dependent activation and reduction sequence.
PMID:10613872
P. aeruginosa CysH supports the alternative direct APS-to-sulfite route.
PMID:9653199
Plant APS reductase supplies the direct glutathione-fed reduction step.
PMID:20424176
Plant sulfur-flux perturbation and complementation ground the downstream sulfite-reduction step.
Part 1: sulfate activation
Sulfate activation to APSReactionsulfate_activation_step
Variant set: ATP sulfurylase architecture by enzyme architecture (Exactly One)

The represented CysD/CysN architecture couples GTP turnover to APS formation. Separate fungal and plant sulfurylase exemplars supply the same chemical activation without requiring that GTPase partner. Oligomeric state is enzyme-specific: the yeast MET3 structure is hexameric. No single assembly is imposed on all homologs. EXACTLY_ONE selects one implementation for a concrete reaction instance, not mutually exclusive gene repertoires across an entire organism.

GTP-coupled CysD/CysN ATP sulfurylaseProtein Complexcysdn_heterodimeric_variant

CysD and CysN form the interacting catalytic/GTPase unit. This does not impose a single heterodimer as the complete holoenzyme: higher-order CysD/CysN assemblies are reported for E. coli, while the structural comparison used P. syringae.

Annotons

CysD/CysN ATP sulfurylase
cysdn_atp_sulfurylase
Participant: Protein Complex: proteobacterial CysD/CysN ATP sulfurylase
Protein Complex:
proteobacterial CysD/CysN ATP sulfurylase Heteromeric sulfate adenylyltransferase with a CysD nucleotidyltransferase subunit and a regulatory CysN GTPase. The interacting CysD/CysN pair is distinguished from higher-order holoenzyme stoichiometry.
Active units:
CysD sulfate adenylyltransferase subunit 2
Participant: Family: CysD sulfate adenylyltransferase subunit 2 family
Family:
CysD sulfate adenylyltransferase subunit 2 familyPANTHER:PTHR43196:SF1
Representative Members: cysD (Pseudomonas putida KT2440)UniProtKB:Q88NA9 cysD (Escherichia coli K-12)UniProtKB:P21156
Role: Catalytic ATP-utilizing sulfate-adenylation subunit.
Function:
sulfate adenylyltransferase (ATP) activityGO:0004781
CysN regulatory GTPase subunit
Participant: Family: CysN sulfate adenylyltransferase regulatory subunits
Family:
CysN sulfate adenylyltransferase regulatory subunitsNCBIfam:TIGR02034
Representative Members: cysNC (Pseudomonas putida KT2440)UniProtKB:Q88NA8 cysN (Escherichia coli K-12)UniProtKB:P23845
NCBIfam TIGR02034 (CysN) is the signature integrated into InterPro IPR011779; both representatives carry it. PANTHER places these proteins in the translation-factor superfamily PTHR23115, whose subfamily SF170 also holds eukaryotic eEF1A, so no PANTHER id is used here (see the PTHR23115 family review). CysNC Q88NA8 contains a C-terminal APS-kinase-like domain as well as the CysN GTPase module. This ATP-sulfurylase unit uses its supported GTPase contribution; domain presence alone does not assert a functional PAPS-reduction route in KT2440.
Role: Couples GTP hydrolysis to APS formation by CysD.
Function:
GTPase activityGO:0003924

Function

sulfate adenylyltransferase (ATP) activityGO:0004781
Substrates: sulfate ATP proton
Products: adenosine 5'-phosphosulfate diphosphate

Forms APS as the activated sulfate intermediate.

PMID:16387658
Pseudomonas syringae CysD/CysN structure and biochemistry establish GTP-coupled sulfate activation; transfer to the listed E. coli and P. putida representatives is comparative, not the assayed strain identity.
Homo-oligomeric Sat/Met3-type ATP sulfurylaseReactionhomooligomeric_sat_variant

Annotons

Homo-oligomeric ATP sulfurylase
met3_type_atp_sulfurylase
Participant: Family: Sat/Met3-type sulfate adenylyltransferases
Family:
Sat/Met3-type sulfate adenylyltransferases
Representative Members: MET3 (Saccharomyces cerevisiae)UniProtKB:P08536 sua1 (Schizosaccharomyces pombe)UniProtKB:P78937 APS1 (Arabidopsis thaliana)UniProtKB:Q9LIK9
Required Function:
sulfate adenylyltransferase (ATP) activityGO:0004781

Function

sulfate adenylyltransferase (ATP) activityGO:0004781
Substrates: sulfate ATP
Products: adenosine 5'-phosphosulfate diphosphate

Forms APS as the activated sulfate intermediate.

PMID:11157739
Yeast MET3 structure establishes a homohexameric sulfurylase.
PMID:18388974
S. pombe sua1 complements the yeast met3 mutation.
PMID:24027241
Arabidopsis At3g22890 expression variation and disruption alter sulfurylase activity and sulfate-assimilation flux.
PMID:7487067
Arabidopsis sulfurylase cDNAs complement yeast mutants; recombinant APS3 supplies family-level structural/kinetic comparison, not an APS1-specific purified assay.
Part 2: reduction of activated sulfate to sulfite
Reduction of activated sulfate to sulfiteMetabolic Pathwayaps_reduction_step

APS may be reduced directly or first phosphorylated to PAPS. Substrate specificity and redox architecture are independent properties: the plant APS reductase uses glutathione through a fused redox domain, whereas the represented bacterial APS and fungal PAPS enzymes use external redox proteins.

Variant set: APS versus PAPS reduction route by substrate route (One Or More)

ONE_OR_MORE permits demonstrated complete routes to coexist. APS kinase alone does not establish the PAPS-reduction route: plants and bacteria can make PAPS for sulfation while using APS reductase for assimilation. A PAPS-reductase activity must also be established.

Bacterial APS reduction with external redox partnerReactiondirect_aps_reduction_route

Annotons

Thioredoxin-dependent APS reductase
cysH_aps_reductase
Participant: Family: CysH APS reductases
Family:
CysH APS reductasesNCBIfam:TIGR02055
Representative Members: cysH (Pseudomonas putida KT2440)UniProtKB:Q88KG2 cysH (Pseudomonas aeruginosa PAO1)UniProtKB:O05927
Required Function:
adenylyl-sulfate reductase (thioredoxin) activityGO:0043866
NCBIfam TIGR02055 (adenylylsulfate reductase, thioredoxin dependent; integrated into InterPro IPR011798) is carried by both representatives, which PANTHER places in PTHR46482:SF9 together with plant APR1 (see the PTHR46482 family review). The reductase family/domain identifies a catalytic class, not the electron donor. The external-thioredoxin reaction is supported by P. aeruginosa biochemistry and transferred to KT2440 by orthology; it is not conferred by this domain alone.

Function

adenylyl-sulfate reductase (thioredoxin) activityGO:0043866
Substrates: adenosine 5'-phosphosulfate reduced thioredoxin
Products: sulfite AMP oxidized thioredoxin

Reduces APS directly to sulfite; external thioredoxin supports the represented bacterial reaction. This donor architecture is not assigned to plant APR merely from the shared reductase fold.

PMID:10613872
Purified P. aeruginosa CysH reduces APS rather than PAPS; the paper distinguishes it from E. coli CysH and from the fused plant APR architecture.
Plant glutathione-dependent APS reductionReactionplant_gsh_aps_reduction_route
Context
Arabidopsis thalianaNCBITaxon:3702

Annotons

Plant APR1 glutathione-dependent APS reductase
apr1_glutathione_aps_reductase
Participant: Family: plant APR1-type APS reductases with fused redox domain
Family:
plant APR1-type APS reductases with fused redox domainPANTHER:PTHR46482:SF9
Representative Members: APR1 (Arabidopsis thaliana)UniProtKB:P92979
Required Function:
adenylyl-sulfate reductase (glutathione) activityGO:0033741
PTHR46482:SF9 also contains bacterial APS reductases. Selection here additionally requires glutathione-fed APS reduction and the plant fused redox-domain architecture; the official subfamily name alone is insufficient.

Function

adenylyl-sulfate reductase (glutathione) activityGO:0033741
Substrates: adenosine 5'-phosphosulfate glutathione
Products: AMP sulfite glutathione disulfide

Locations

chloroplastGO:0009507

The reductase domain and fused C-terminal glutaredoxin-like redox domain cooperate in APS reduction. Glutathione supplies reducing equivalents; a separate thioredoxin protein is not required by this demonstrated reaction.

PMID:9653199
Purified APR1 uses glutathione; separated catalytic and redox domains partially reconstitute APS reduction when mixed.
PMID:30825314
Comparative plant synthesis contextualizes plastid APR architecture and its distinction from PAPS reductases.
PAPS route (APS kinase then PAPS reductase)Metabolic Pathwaypaps_reduction_route

APS kinase phosphorylates APS to PAPS, which a thioredoxin-dependent PAPS reductase reduces to sulfite and adenosine 3',5'-bisphosphate. MET3 plus MET14 is also the PAPS-generating sulfate activation used for sulfonation (YeastPathways PWY-5340).

Connections

APS kinase supplies PAPS to PAPS reductase.
PMID:1654509
MET14 encodes the APS-phosphorylating enzyme.
PMID:2203779
MET16 encodes the PAPS-consuming reductase, supporting substrate continuity between the reactions.
Part 1: APS phosphorylation
APS kinaseReactionaps_kinase_step

Annotons

Adenylyl-sulfate kinase
aps_kinase_activity
Participant: Family: APS kinase / PAPS synthase family
Family:
APS kinase / PAPS synthase family
Representative Members: MET14 (Saccharomyces cerevisiae)UniProtKB:Q02196 met14 (Schizosaccharomyces pombe)UniProtKB:Q9P7G9 CysC (Escherichia coli K-12)UniProtKB:P0A6J1
Required Function:
adenylylsulfate kinase activityGO:0004020
PTHR11055 is named for the animal bifunctional PAPS synthases but also contains monofunctional APS kinases (MET14 and S. pombe met14 in SF1, E. coli CysC in SF63).

Function

adenylylsulfate kinase activityGO:0004020
Substrates: adenosine 5'-phosphosulfate ATP
Products: 3'-phosphoadenosine 5'-phosphosulfate ADP

Phosphorylates APS at the 3'-hydroxyl to PAPS.

PMID:1654509
Cloned yeast MET14 encodes APS kinase. The PAPS-reduction route requires this phosphorylation before PAPS reductase.
Part 2: PAPS reduction to sulfite
Thioredoxin-dependent PAPS reductionReactionpaps_reduction_step

Annotons

PAPS reductase
paps_reductase_activity
Participant: Family: PAPS reductases
Family:
PAPS reductasesPANTHER:PTHR46509:SF1
Representative Members: MET16 (Saccharomyces cerevisiae)UniProtKB:P18408 met16 (Schizosaccharomyces pombe)UniProtKB:Q10270 CysH (Escherichia coli K-12)UniProtKB:P17854
Required Function:
phosphoadenylyl-sulfate reductase (thioredoxin) activityGO:0004604

Function

phosphoadenylyl-sulfate reductase (thioredoxin) activityGO:0004604
Substrates: 3'-phosphoadenosine 5'-phosphosulfate reduced thioredoxin
Products: sulfite adenosine 3',5'-bisphosphate oxidized thioredoxin

Reduces PAPS to free sulfite using thioredoxin.

PMID:2203779
MET16 is the yeast structural gene for PAPS reductase, related to E. coli CysH.
PMID:3060034
Purified yeast PAPS reductase uses reduced thioredoxin as cosubstrate.
Thioredoxin reductant for PAPS reductase
thioredoxin_electron_donor
Participant: Family: cytosolic thioredoxins
Family:
cytosolic thioredoxins
Representative Members: TRX1 (Saccharomyces cerevisiae)UniProtKB:P22217 TRX2 (Saccharomyces cerevisiae)UniProtKB:P22803 trx1 (Schizosaccharomyces pombe)UniProtKB:O14463
No PANTHER ID is asserted because the release-pinned classification places these representatives in PTHR10438:SF468 whereas their UniProt cross-references report PTHR46115. The explicit member identities and electron-donor role delimit this selector; a surprising official family name is not by itself evidence against membership.

Function

protein-disulfide reductase activityGO:0015035 Reduced thioredoxin supplies reducing equivalents to the characterized PAPS-reductase system and is regenerated by NADPH-thioredoxin reductase outside the module. The purified yeast assay requires it, but low-oxidant native growth conditions permit an unidentified alternative donor.

Supplies reducing equivalents for the characterized thioredoxin-fed PAPS reductase system. Yeast double-mutant requirements depend on oxidative conditions; low-ROS sulfate assimilation and an unidentified alternative donor have been reported, so glutaredoxin exclusion is not universalized.

PMID:2026619
The tested yeast trx1 trx2 double deletion is methionine auxotrophic.
PMID:10844700
Under low aeration and without functional mitochondria, strains lacking both thioredoxins can assimilate sulfate; the alternative hydrogen donor remains unidentified.

Connections

Reduced thioredoxin supplies reducing equivalents in the characterized PAPS reductase reaction; this edge is not a universal exclusive donor requirement under every growth condition.
PMID:3060034
Purified enzyme requires reduced thioredoxin in the reported assays.
PMID:10844700
Native donor requirements depend on growth and oxidative conditions.
Part 3: sulfite reduction
Assimilatory reduction of sulfite to sulfideReactionsulfite_reduction_step
Variant set: Sulfite-reductase electron-donor architecture by electron-supply architecture (Exactly One)

Donor architecture is selected by target evidence, not by broad siroheme-reductase family labels. The Pseudomonas Fpr-linked route has an unresolved intervening carrier; the ferredoxin-linked route, enterobacterial diflavin complex and fungal hemoflavoprotein are distinct implementations. Cofactor synthesis and reductant regeneration are outside the minimal boundary. EXACTLY_ONE selects one implementation for a concrete reaction instance, not mutually exclusive gene repertoires across an entire organism.

Pseudomonas Fpr-linked sulfite reductionReactionpseudomonas_fpr_cysi_route

Genetic evidence links FprA to efficient sulfite reduction in pseudomonads. The immediate physiological carrier to CysI is unresolved; flavodoxin and ferredoxin capacities cannot be equated with demonstrated native pairing.

Annotons

Pseudomonas CysI sulfite reduction
pseudomonas_cysi_activity
Participant: Family: ferredoxin sulfite/nitrite reductase family
Family:
ferredoxin sulfite/nitrite reductase familyPANTHER:PTHR32439
Representative Members: cysI (Pseudomonas putida KT2440)UniProtKB:Q88KB9
PTHR32439 contains both sulfite and nitrite reductases. The Pseudomonas sulfite-reduction role is supported comparatively; neither this family label nor FprA dependence establishes the immediate native electron carrier.

Function

sulfite reduction with unresolved physiological electron donorGO:0016667 GO:0016667 is the donor-neutral sulfur-redox parent used in the KT2440 cysI gene review. The former generic sulfite-reductase grouping (GO:0016002) is obsolete, and a donor-specific term such as GO:0050311 would exceed the evidence while the immediate carrier is unresolved.
Substrates: sulfite
Products: sulfide

Catalytic hemoprotein in the inferred Pseudomonas sulfite-reduction system; immediate carrier identity remains unresolved.

PMID:23794620
FinR/FprA perturbation and E. coli CysJI complementation locate the defect at sulfite reduction; the primary genetic host is P. putida DSM 3601, not KT2440.
Fpr electron supply
fpr_electron_supply
Participant: Family: bacterial type-1 ferredoxin--NADP reductases
Family:
bacterial type-1 ferredoxin--NADP reductasesPANTHER:PTHR47878:SF1
Representative Members: fpr-I (Pseudomonas putida KT2440)UniProtKB:Q88MD5

Function

ferredoxin-NADP+ reductase activityGO:0004324

Fpr-I is the KT2440 type-1 reductase ortholog linked to electron supply for sulfite reduction. Regeneration of the actual CysI donor remains a mechanistic hypothesis, not a demonstrated ferredoxin-specific coupling.

PMID:23794620
Genetic rescue supports a sulfur-assimilation role for FprA; it does not identify the intervening carrier. Biochemical preferences discussed in the full text favor flavodoxin for FprA and ferredoxin for FprB.

Connections

Proposed electron-supply relationship supported by genetic complementation; the intervening carrier is not identified.
PMID:23794620
E. coli CysJI bypasses the reduced FprA-expression phenotype, supporting electron-supply architecture without proving a direct molecular handoff.
Ferredoxin-linked sulfite reductionReactionferredoxin_sulfite_reduction_route

The plant enzyme and mycobacterial SirA belong to the ferredoxin-linked sulfite-reductase class. For SirA, this is a structural/class assignment: both cited purified-enzyme studies used methyl viologen, and neither identified the physiological ferredoxin partner. The plant native-flux study also used reduced-dye activity assays; biochemical donor architecture must be supported separately from native loss-of-function phenotypes. Maize SiR-Fd structural and mutational studies provide independent direct support for the plant donor mechanism, transferred comparatively to Arabidopsis.

Annotons

Ferredoxin-linked sulfite reductase
ferredoxin_sulfite_reductase
Participant: Family: siroheme sulfite-reductase families with ferredoxin-linked implementations
Family:
siroheme sulfite-reductase families with ferredoxin-linked implementations
Representative Members: sir (Mycobacterium tuberculosis H37Rv)UniProtKB:P9WJ03 SIR (Arabidopsis thaliana)UniProtKB:Q9LZ66
Required Function:
sulfite reductase (ferredoxin) activityGO:0050311
Official family labels do not identify actual electron donor: the plant SIR is classified with a subfamily named NADPH subunit beta. Use protein-specific evidence and domain architecture.

Function

sulfite reductase (ferredoxin) activityGO:0050311 The ferredoxin-linked enzyme-class reaction is represented here. Native partner identity and direct physiological pairing are not established by the SirA methyl-viologen assays.
Substrates: sulfite reduced ferredoxin
Products: sulfide oxidized ferredoxin water

Reduces sulfite to sulfide at siroheme and iron-sulfur cofactors. Reduced ferredoxin supply is a boundary input and is not universally assigned to the bacterial Fpr-I exemplar.

PMID:15917234
H37Rv NirA/SirA structure and methyl-viologen-supported mutagenesis establish sulfite-reductase chemistry; external ferredoxin binding is proposed from structural comparison, not measured native pairing.
PMID:17644602
Purified M. tuberculosis SirA prefers sulfite over nitrite using methyl viologen; native deletion/rescue tests used M. smegmatis.
PMID:20424176
Arabidopsis SIR mutation, complementation and sulfur-flux analysis establish the plant assimilatory role. Biochemical donor assignment must be distinguished from reduced-dye activity measurements.
PMID:26920048
Maize SiR-Fd co-crystals and interface mutants directly connect binding to ferredoxin-dependent activity. This supplies comparative plant donor evidence, not an Arabidopsis-specific pairing assay.
PMID:11132635
Review of maize enzyme and ferredoxin-mutant biochemistry provides plant donor-mechanism context, distinguished from the Arabidopsis native-flux experiment.
CysJ/CysI NADPH-dependent routeReactioncysji_nadph_route

The classical enterobacterial implementation uses a CysJ diflavin subunit to transfer electrons from NADPH to the CysI siroheme/iron-sulfur catalytic subunit. The reported alpha8beta4 reconstitution differs from the alpha8beta8 assembly stated in the current UniProt subunit notes; the module attributes the count to the experiment rather than imposing it on every preparation.

Annotons

CysJ/CysI NADPH sulfite reductase
cysji_nadph_sulfite_reductase
Participant: Protein Complex: CysJ/CysI sulfite reductase complex
Protein Complex:
CysJ/CysI sulfite reductase complexGO:0009337
Active units:
CysJ flavoprotein electron-transfer subunit
Participant: Family: CysJ NADPH sulfite-reductase flavoproteins
Family:
CysJ NADPH sulfite-reductase flavoproteinsPANTHER:PTHR19384:SF128
Representative Members: cysJ (Escherichia coli K-12)UniProtKB:P38038
Role: Transfers electrons from NADPH to CysI.
CysI hemoprotein catalytic subunit
Participant: Family: NADPH-dependent CysI hemoproteins
Family:
NADPH-dependent CysI hemoproteinsPANTHER:PTHR11493:SF47
Representative Members: cysI (Escherichia coli K-12)UniProtKB:P17846
Required Function:
contribution to sulfite reductase (NADPH) activityGO:0004783
PTHR11493:SF47 also contains plant ferredoxin-linked SIR. This role requires contribution to the NADPH-dependent complex with the specified flavoprotein partner; membership alone neither identifies the donor nor makes the isolated hemoprotein an NADPH-binding enzyme.
Role: Reduces sulfite at the siroheme/iron-sulfur center.

Function

sulfite reductase (NADPH) activityGO:0004783
Substrates: sulfite NADPH proton
Products: sulfide NADP+ water

Performs NADPH-dependent reduction of sulfite to sulfide.

PMID:26088143
Recombinant E. coli CysJ/CysI reconstitution supports NADPH-dependent sulfite reduction and the reported alpha8beta4 holoenzyme; isolated hemoprotein dye reduction is distinct from complete NADPH-linked catalysis.
PMID:40140349
The engineered minimal E. coli flavoprotein/hemoprotein complex reveals the binding interface and domain requirements. Its heterodimeric construct is not substituted for native holoenzyme stoichiometry.
Fungal Met10/Met5 NADPH sulfite reductaseReactionmet10_met5_nadph_route

Fungal NADPH-dependent hemoflavoprotein with a reported alpha2beta2 assembly in the purified yeast system. Met10 carries FAD/NADPH-related architecture; positive flavodoxin-domain evidence lies on Met5 rather than Met10, supporting an FMN-domain distribution distinct from bacterial CysJ. This domain inference is not represented as an isolated-subunit FMN-binding measurement. Both subunits contribute to the complex activity.

Annotons

Met10/Met5 NADPH sulfite reductase
met10_met5_nadph_sulfite_reductase
Participant: Protein Complex: fungal Met10/Met5 sulfite reductase complex
Protein Complex:
fungal Met10/Met5 sulfite reductase complexGO:0009337
Active units:
Met10 flavoprotein alpha subunit
Participant: Family: fungal sulfite reductase flavoprotein components
Family:
fungal sulfite reductase flavoprotein componentsPANTHER:PTHR19384:SF109
Representative Members: MET10 (Saccharomyces cerevisiae)UniProtKB:P39692 met10 (Schizosaccharomyces pombe)UniProtKB:Q09878
Role: Transfers electrons from NADPH to the Met5 hemoprotein.
Met5 hemoprotein beta subunit
Participant: Family: NADPH sulfite reductase hemoproteins
Family:
NADPH sulfite reductase hemoproteinsPANTHER:PTHR11493:SF47
Representative Members: MET5 (Saccharomyces cerevisiae)UniProtKB:P47169 sir1 (Schizosaccharomyces pombe)UniProtKB:Q1K9C2
Required Function:
contribution to sulfite reductase (NADPH) activityGO:0004783
PTHR11493:SF47 also contains plant ferredoxin-linked SIR. This role requires contribution to the NADPH-dependent complex with the specified flavoprotein partner; membership alone neither identifies the donor nor makes the isolated hemoprotein an NADPH-binding enzyme.
Role: Reduces sulfite at the siroheme/iron-sulfur center.

Function

sulfite reductase (NADPH) activityGO:0004783
Substrates: sulfite NADPH proton
Products: hydrogen sulfide NADP+ water

Performs the NADPH-dependent six-electron reduction of sulfite to sulfide; requires siroheme from siroheme_biosynthesis (met1 and met8 mutants lack the activity, PMID:1479340).

PMID:6751400
Purified yeast sulfite reductase supports a two-subunit alpha2beta2 hemoflavoprotein model.
PMID:7928966
MET10 sequence and expression identify the alpha component, including FAD/NADPH-related features but no obvious FMN-binding motif.
PMID:1479340
Native yeast mutant analysis identifies MET5 and MET10 requirements alongside siroheme-biosynthetic genes.
PMID:11319255
Figure 3F/G and Results place the FMN domain on yeast MET5/P47169 and FAD/NADP modules on MET10. The exact primary passages are preserved in the cited reproducible source-analysis artifact; the PMID cache remains abstract-only. The old S. pombe accession is not silently equated to current Q1K9C2.
file:yeast/MET5/MET5-source-analysis/README.md
The primary Results place an FMN domain upstream of the PuSR hemoprotein domain; this is sequence/domain evidence rather than an isolated-subunit binding assay.
PuSR encodes a translational fusion of PFO domains I, II (partial), and VI with the FMN domain of CPR, which, in turn, is fused to a hemoprotein domain (fig. 3F ).
file:yeast/MET5/MET5-source-analysis/README.md
The accompanying Figure 3F/G legend explicitly identifies the yeast PuSR target as P47169 and distinguishes MET10.
F, Conservation between PNO and putative sulfite reductase from Saccharomyces cerevisiae (PuSR; P47169) and Schizosaccharomyces pombe (014167). G, Sulfite reductase α-subunit (MET10) from yeast (L26504) and S. pombe (T41439).