PAPS biosynthesis and Golgi import (sulfate activation) (PAPSS1/2 -> SLC35B2/3)

Sulfation of biomolecules requires an activated sulfonate donor, 3'-phosphoadenosine 5'-phosphosulfate (PAPS), the universal substrate of every cytosolic and Golgi-lumenal sulfotransferase (sulfation of glycosaminoglycans/proteoglycans, glycolipids, steroids and DHEA, thyroid hormone, catecholamines, tyrosine residues and xenobiotics). PAPS is made in two steps by a single bifunctional enzyme, PAPS synthase (PAPSS1, ubiquitous; PAPSS2, predominant in cartilage): an ATP sulfurylase (sulfate adenylyltransferase) domain condenses inorganic sulfate with ATP to adenosine 5'-phosphosulfate (APS) + pyrophosphate, and an APS kinase (adenylyl-sulfate kinase) domain phosphorylates APS with a second ATP to PAPS + ADP. The cytosolic PAPS pool feeds cytosolic sulfotransferases directly, and is imported into the Golgi lumen by the antiporters SLC35B2 (PAPST1) and SLC35B3 (PAPST2), which exchange cytosolic PAPS for lumenal PAP (adenosine 3',5'-bisphosphate, the spent product), supplying the Golgi sulfotransferases that sulfate secreted and membrane glycoconjugates. Defects illustrate the pathway's importance: biallelic PAPSS2 mutations cause spondyloepimetaphyseal dysplasia (Pakistani-type brachyolmia) and androgen excess through defective proteoglycan and DHEA sulfation.

MODULE:paps_sulfate_activationDRAFTMetabolic Pathwaymodules/paps_sulfate_activation.yaml
3'-phosphoadenosine 5'-phosphosulfate biosynthetic processGO:0050428 sulfate assimilationGO:0000103 3'-phospho-5'-adenylyl sulfate transmembrane transportGO:1902559
GO:0050428
3'-phosphoadenosine 5'-phosphosulfate biosynthetic process
PAPSS1/PAPSS2 synthesise the activated sulfonate donor PAPS (GO:0050428).
GO:0000103
sulfate assimilation
The pathway assimilates inorganic sulfate into PAPS for transfer reactions (GO:0000103).
GO:1902559
3'-phospho-5'-adenylyl sulfate transmembrane transport
SLC35B2/SLC35B3 import PAPS into the Golgi lumen (GO:1902559).
file:human/PAPSS1/PAPSS1-ai-review.yaml
PAPSS1 gene review (human)
Bifunctional PAPS synthase 1 (UniProtKB:O43252, GO:0004781/GO:0004020) matches the completed human PAPSS1 review.
file:human/PAPSS2/PAPSS2-ai-review.yaml
PAPSS2 gene review (human)
Bifunctional PAPS synthase 2 (UniProtKB:O95340, GO:0004781/GO:0004020) matches the completed human PAPSS2 review.
file:human/SLC35B2/SLC35B2-ai-review.yaml
SLC35B2 gene review (human)
Golgi PAPS transporter 1 / PAPST1 (UniProtKB:Q8TB61, GO:0046964) matches the completed human SLC35B2 review.
file:human/SLC35B3/SLC35B3-ai-review.yaml
SLC35B3 gene review (human)
Golgi PAPS transporter 2 / PAPST2 (UniProtKB:Q9H1N7, GO:0046964) matches the completed human SLC35B3 review.
3Nodes
2Parts
0Variant Sets
0Variants
3Annotons
1Connections

Derived QC

Recommended-field compliance

100.0% recommended fields populated

All recommended fields populated.

Module deep research

✗ none found

No MODULE:paps_sulfate_activation deep-research report alongside the module YAML.

Leaf nodes lacking representative members

✓ every leaf node grounds to a representative protein.

Template conformance

✓ every declared conforms_to bundle matches its template motif.

Gene-review completeness (4/4 grounded genes reviewed)

4 complete review(s) · 0 with deep research · 0 missing review · 4 reviewed but lacking deep research

Gene Review Complete Deep research
PAPSS1 O43252 ✓ ✓ ✗
PAPSS2 O95340 ✓ ✓ ✗
SLC35B2 Q8TB61 ✓ ✓ ✗
SLC35B3 Q9H1N7 ✓ ✓ ✗

Details

Context
cytosolGO:0005829 Golgi membraneGO:0000139
PAPS biosynthesis and Golgi import (sulfate activation)Metabolic Pathwaypaps_sulfate_activation
3'-phosphoadenosine 5'-phosphosulfate biosynthetic processGO:0050428 sulfate assimilationGO:0000103 3'-phospho-5'-adenylyl sulfate transmembrane transportGO:1902559
Context
cytosolGO:0005829 Golgi membraneGO:0000139

PAPS biosynthesis and Golgi import / sulfate activation (GO:0050428 + GO:1902559), grounded to four completed human gene reviews. PAPS is the universal sulfonate donor for all sulfotransferases. Synthesis: the bifunctional PAPS synthases PAPSS1 (O43252, ubiquitous) and PAPSS2 (O95340, cartilage-predominant), both PTHR11055, carry two domains modelled as two annotons on one node — ATP sulfurylase (GO:0004781; sulfate + ATP -> APS + PPi) and APS kinase (GO:0004020; APS + ATP -> PAPS + ADP), both cytosolic (GO:0050428 / GO:0000103). Golgi delivery: SLC35B2/PAPST1 (Q8TB61) and SLC35B3/PAPST2 (Q9H1N7), both PTHR10778, are Golgi-membrane PAPS:PAP antiporters (GO:0046964 / GO:1902559) supplying lumenal sulfotransferases. Curation notes from the reviews: SLC35B2's APS-transport (GO:1902558) TAS was corrected to the PAPS term GO:1902559 (APS is the precursor, not the transported substrate), and an ER-membrane IBA was corrected to Golgi (family over-propagation); SLC35B3 had the same APS-vs-PAPS metabolite mismatch flagged; PAPSS1's skeletal-dysplasia TAS actually concerns the paralog PAPSS2 (flagged MISCITED). PAPSS2 LOF -> spondyloepimetaphyseal dysplasia (Pakistani-type brachyolmia) + androgen excess (DHEA under- sulfation). GO term ids/labels verified against the local go.db; module passes structural + term-label validation.

Connections

paps_synthesis -> paps_golgi_import Provides Input For
The cytosolic PAPS made by PAPSS1/2 is imported into the Golgi by SLC35B2/B3.
Part 1: PAPS biosynthesis (sulfate + 2 ATP -> PAPS)
Bifunctional PAPS synthase (PAPSS1 / PAPSS2)Reactionpaps_synthesis

Annotons

PAPSS1/2: ATP sulfurylase domain (sulfate + ATP -> APS)
papss_atp_sulfurylase
Participant: Family: PAPSS / bifunctional PAPS synthase family
Family:
PAPSS / bifunctional PAPS synthase familyPANTHER:PTHR11055
Representative Members: PAPSS1 (human; ubiquitous)UniProtKB:O43252 PAPSS2 (human; cartilage-predominant)UniProtKB:O95340

Function

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

Locations

cytosolGO:0005829

Condense inorganic sulfate with ATP to APS.

PAPSS1/2: APS kinase domain (APS + ATP -> PAPS)
papss_aps_kinase
Participant: Family: PAPSS / bifunctional PAPS synthase family
Family:
PAPSS / bifunctional PAPS synthase familyPANTHER:PTHR11055
Representative Members: PAPSS1 (human)UniProtKB:O43252 PAPSS2 (human)UniProtKB:O95340

Function

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

Locations

cytosolGO:0005829

Phosphorylate APS with ATP to the activated donor PAPS.

Part 2: Golgi PAPS import (PAPS/PAP antiport)
Golgi PAPS transporter (SLC35B2 / SLC35B3)Reactionpaps_golgi_import

Annotons

SLC35B2/SLC35B3: Golgi PAPS transporter (PAPST1/2)
slc35b_activity
Participant: Family: SLC35B nucleotide-sugar/PAPS transporter family
Family:
SLC35B nucleotide-sugar/PAPS transporter familyPANTHER:PTHR10778
Representative Members: SLC35B2 / PAPST1 (human)UniProtKB:Q8TB61 SLC35B3 / PAPST2 (human)UniProtKB:Q9H1N7

Function

3'-phosphoadenosine 5'-phosphosulfate transmembrane transporter activityGO:0046964
Substrates: PAPS (cytosolic; antiport with lumenal PAP)
Products: PAPS (Golgi lumen)

Locations

Golgi membraneGO:0000139

Import cytosolic PAPS into the Golgi lumen (exchange for PAP).