Existing Annotations Review

GO Term	Evidence	Action	Reason
GO:0004145 diamine N-acetyltransferase activity	IEA GO_REF:0000120	ACCEPT	Summary: Diamine N-acetyltransferase activity (EC 2.3.1.57) from the combined IEA pipeline. Human SAT1 N1-acetylates spermidine and spermine using acetyl-CoA. Reason: The defining activity of SAT1, experimentally established for the human enzyme (kinetics and a bisubstrate-inhibitor crystal structure, PMID:17516632). Transfer to donkey is grounded phylogenetically, not just by similarity - the donkey protein is classified in the SAT1 subfamily PTHR10545:SF36, and PAINT placed GO:0004145 at the vertebrate SAT1 node PTN002576187 (seeded by human, mouse and zebrafish SAT1), whose descendants include this ortholog. It is a full-length 171-aa product, 97% identical to human SAT1, with the general acid Tyr140 and general base Glu92 conserved; it is only 45% identical to SAT2 (SF51), whose kcat/Km for polyamines is negligible, so the subfamily boundary matters and the donkey sits on the SAT1 side. Supporting Evidence: PMID:17516632 The N1-acetylation of spermidine and spermine by spermidine/spermine file:human/SAT1/SAT1-uniprot.txt Enzyme which catalyzes the acetylation of polyamines file:EQUAS/SAT1/SAT1-bioinformatics/RESULTS.md The human catalytic Tyr140 is conserved (donkey Tyr140) file:EQUAS/SAT1/SAT1-bioinformatics/RESULTS-rereview.md donkey_SAT1 vs human_SAT2 (Q96F10, 170 aa): 77/170 identical paired residues = 45.3% file:EQUAS/SAT1/SAT1-uniprot.txt DR PANTHER; PTHR10545:SF36; DIAMINE ACETYLTRANSFERASE 1; 1.
GO:0005737 cytoplasm	IEA GO_REF:0000044	MODIFY	Summary: Cytoplasm from the UniProt location mapping (ARBA-derived). Human SAT1 is a soluble cytosolic enzyme. Reason: Correct but less specific than the established location; the human enzyme is assigned to the cytosol, which is the appropriate compartment for a soluble acetyl-CoA-dependent polyamine acetyltransferase. Proposed replacements: cytosol Supporting Evidence: file:human/SAT1/SAT1-uniprot.txt SUBCELLULAR LOCATION: Cytoplasm, cytosol
GO:0006595 polyamine metabolic process	IEA GO_REF:0000117	MODIFY	Summary: ARBA assignment of polyamine metabolic process. SAT1 catalyses the rate-limiting step of polyamine catabolism. Reason: The essence is correct, but SAT1 acts specifically in the catabolic branch (N1-acetylation committing spermidine and spermine to export or oxidative back-conversion), and it catalyses the first step of both spermidine and spermine catabolism. Polyamine catabolic process and its two substrate-specific descendants are the informative terms, matching the human SAT1 review. The paralog SAT2 was shown not to be a polyamine catabolic enzyme, so this process is a SAT1-subfamily property; the donkey protein is in that subfamily. Proposed replacements: polyamine catabolic process spermidine catabolic process spermine catabolic process Supporting Evidence: PMID:1985966 rate-limiting enzyme in the catabolism of polyamines PMID:17516632 The N1-acetylation of spermidine and spermine by spermidine/spermine PMID:15283699 These results indicate that SSAT2 is not a polyamine catabolic enzyme
GO:0008080 N-acetyltransferase activity	IEA GO_REF:0000118	TOO GENERAL	Summary: TreeGrafter transfer of N-acetyltransferase activity (TreeGrafter node PTN008947708; PAINT placed this term at the family-root node PTN000057452). Reason: True (SAT1 is an N-acetyltransferase) but entailed by diamine N-acetyltransferase activity, accepted in this review.
GO:0016407 acetyltransferase activity	IEA GO_REF:0000104	TOO GENERAL	Summary: UniRule assignment of acetyltransferase activity. Reason: True but uninformative; entailed by diamine N-acetyltransferase activity.
GO:0016740 transferase activity	IEA GO_REF:0000104	TOO GENERAL	Summary: UniRule assignment of transferase activity. Reason: True but uninformative; entailed by diamine N-acetyltransferase activity.
GO:0016747 acyltransferase activity, transferring groups other than amino-acyl groups	IEA GO_REF:0000002	TOO GENERAL	Summary: InterPro2GO mapping from the GNAT domain. Reason: True for a GNAT acetyltransferase but uninformative; entailed by diamine N-acetyltransferase activity.
GO:0019809 spermidine binding	IEA GO_REF:0000118	KEEP AS NON CORE	Summary: TreeGrafter transfer of spermidine binding (IBA in human SAT1, from PAINT node PTN002576187 seeded by rat Sat1). Reason: SAT1 binds spermidine as its preferred substrate, so the term is correct and is as precise as the evidence allows, but substrate binding is part of the catalytic activity rather than a separate function; kept as non-core, consistent with the human review. The single-seed PAINT node is not a weakness. Supporting Evidence: file:human/SAT1/SAT1-uniprot.txt norspermidine = spermidine >> spermine

GO Term

Evidence

Action

Reason

GO:0004145 diamine N-acetyltransferase activity

IEA
GO_REF:0000120

Summary: Diamine N-acetyltransferase activity (EC 2.3.1.57) from the combined IEA pipeline. Human SAT1 N1-acetylates spermidine and spermine using acetyl-CoA.

Reason: The defining activity of SAT1, experimentally established for the human enzyme (kinetics and a bisubstrate-inhibitor crystal structure, PMID:17516632). Transfer to donkey is grounded phylogenetically, not just by similarity - the donkey protein is classified in the SAT1 subfamily PTHR10545:SF36, and PAINT placed GO:0004145 at the vertebrate SAT1 node PTN002576187 (seeded by human, mouse and zebrafish SAT1), whose descendants include this ortholog. It is a full-length 171-aa product, 97% identical to human SAT1, with the general acid Tyr140 and general base Glu92 conserved; it is only 45% identical to SAT2 (SF51), whose kcat/Km for polyamines is negligible, so the subfamily boundary matters and the donkey sits on the SAT1 side.

Supporting Evidence:

PMID:17516632

The N1-acetylation of spermidine and spermine by spermidine/spermine

file:human/SAT1/SAT1-uniprot.txt

Enzyme which catalyzes the acetylation of polyamines

file:EQUAS/SAT1/SAT1-bioinformatics/RESULTS.md

The human catalytic Tyr140 is conserved (donkey Tyr140)

file:EQUAS/SAT1/SAT1-bioinformatics/RESULTS-rereview.md

donkey_SAT1 vs human_SAT2 (Q96F10, 170 aa): 77/170 identical paired residues = 45.3%

file:EQUAS/SAT1/SAT1-uniprot.txt

DR PANTHER; PTHR10545:SF36; DIAMINE ACETYLTRANSFERASE 1; 1.

GO:0005737 cytoplasm

IEA
GO_REF:0000044

MODIFY

Summary: Cytoplasm from the UniProt location mapping (ARBA-derived). Human SAT1 is a soluble cytosolic enzyme.

Reason: Correct but less specific than the established location; the human enzyme is assigned to the cytosol, which is the appropriate compartment for a soluble acetyl-CoA-dependent polyamine acetyltransferase.

Proposed replacements: cytosol

Supporting Evidence:

file:human/SAT1/SAT1-uniprot.txt

SUBCELLULAR LOCATION: Cytoplasm, cytosol

GO:0006595 polyamine metabolic process

IEA
GO_REF:0000117

MODIFY

Summary: ARBA assignment of polyamine metabolic process. SAT1 catalyses the rate-limiting step of polyamine catabolism.

Reason: The essence is correct, but SAT1 acts specifically in the catabolic branch (N1-acetylation committing spermidine and spermine to export or oxidative back-conversion), and it catalyses the first step of both spermidine and spermine catabolism. Polyamine catabolic process and its two substrate-specific descendants are the informative terms, matching the human SAT1 review. The paralog SAT2 was shown not to be a polyamine catabolic enzyme, so this process is a SAT1-subfamily property; the donkey protein is in that subfamily.

Proposed replacements: polyamine catabolic process spermidine catabolic process spermine catabolic process

Supporting Evidence:

PMID:1985966

rate-limiting enzyme in the catabolism of polyamines

PMID:17516632

The N1-acetylation of spermidine and spermine by spermidine/spermine

PMID:15283699

These results indicate that SSAT2 is not a polyamine catabolic enzyme

GO:0008080 N-acetyltransferase activity

IEA
GO_REF:0000118

TOO GENERAL

Summary: TreeGrafter transfer of N-acetyltransferase activity (TreeGrafter node PTN008947708; PAINT placed this term at the family-root node PTN000057452).

Reason: True (SAT1 is an N-acetyltransferase) but entailed by diamine N-acetyltransferase activity, accepted in this review.

GO:0016407 acetyltransferase activity

IEA
GO_REF:0000104

TOO GENERAL

Summary: UniRule assignment of acetyltransferase activity.

Reason: True but uninformative; entailed by diamine N-acetyltransferase activity.

GO:0016740 transferase activity

IEA
GO_REF:0000104

TOO GENERAL

Summary: UniRule assignment of transferase activity.

Reason: True but uninformative; entailed by diamine N-acetyltransferase activity.

GO:0016747 acyltransferase activity, transferring groups other than amino-acyl groups

IEA
GO_REF:0000002

TOO GENERAL

Summary: InterPro2GO mapping from the GNAT domain.

Reason: True for a GNAT acetyltransferase but uninformative; entailed by diamine N-acetyltransferase activity.

GO:0019809 spermidine binding

IEA
GO_REF:0000118

KEEP AS NON CORE

Summary: TreeGrafter transfer of spermidine binding (IBA in human SAT1, from PAINT node PTN002576187 seeded by rat Sat1).

Reason: SAT1 binds spermidine as its preferred substrate, so the term is correct and is as precise as the evidence allows, but substrate binding is part of the catalytic activity rather than a separate function; kept as non-core, consistent with the human review. The single-seed PAINT node is not a weakness.

Supporting Evidence:

file:human/SAT1/SAT1-uniprot.txt

norspermidine = spermidine >> spermine

Core Functions

Cytosolic spermidine/spermine N1-acetyltransferase that uses acetyl-CoA to N1-acetylate spermidine and spermine, the rate-limiting step of polyamine catabolism and back-conversion.

Molecular Function:

diamine N-acetyltransferase activity

Directly Involved In:

polyamine catabolic process spermidine catabolic process spermine catabolic process

Cellular Locations:

cytosol

Supporting Evidence:

PMID:17516632
The N1-acetylation of spermidine and spermine by spermidine/spermine
PMID:1985966
rate-limiting enzyme in the catabolism of polyamines
file:EQUAS/SAT1/SAT1-bioinformatics/RESULTS-rereview.md
Human SAT1 catalytic residues (Glu92 general base, Tyr140 general acid) map to donkey Glu92 and Tyr140.

External Prediction Reviews

These computational predictions are reviewed separately from the GOA annotation set used for this review. The assessments below are from this project and do not constitute official GO annotations or endorsement by GO/UniProt. They are not included in the existing annotation review above.

ProtNLM2 External predictions

View prediction review YAML · SAT1-protnlm-predictions-review.yaml · Review status: COMPLETE

Assessment of the single ProtNLM2 GO prediction for donkey SAT1 (A0A9L0KCT9), judged against the donkey GOA record (diamine N-acetyltransferase activity, broader transferase terms, spermidine binding, polyamine metabolic process, cytoplasm), the human ortholog P21673 and its characterization, and a donkey-human alignment (97% identity, catalytic Tyr140 conserved). The prediction, putrescine catabolic process, is not in donkey GOA and is neither established nor refuted by the available evidence, which is conflicting (UNC). Non-GO ProtNLM2 output, not scored - subcellular location 'Nucleus', which conflicts with the cytosolic localization of the human enzyme.

Source documents: projects/PROTNLM_EVALUATION/donkey40/donkey40-predictions.tsv · genes/EQUAS/SAT1/SAT1-goa.tsv · genes/human/SAT1/SAT1-uniprot.txt · genes/EQUAS/SAT1/SAT1-bioinformatics/RESULTS.md

Review score: 2 = concordant with evidence; 1 = uncertain; 0 = discordant with evidence. This is an assessment score, not a model probability.

GO:0009447 putrescine catabolic process GO_BP

UNC — Uncertain Review score: 1/2

Prediction method: ProtNLM2 · Version: UniProt API snapshot 2026-10-14

Review rationale: Not in donkey GOA, which has the broader polyamine metabolic process; the donkey gene review refines that to polyamine, spermidine and spermine catabolic process and leaves putrescine acetylation by SAT1 as an open question. SAT1's established substrates are spermidine and spermine (also norspermidine and 1,3-diaminopropane); their N1-acetylation and oxidation generate putrescine rather than consume it. Purified rat liver SSAT, the inducible SAT1-type enzyme, was inactive with putrescine. Against this, a mouse study attributes N-acetylputrescine production in the gut to Sat1, though without direct enzymology on purified Sat1 with putrescine, and human UniProt maps SAT1 to the UniPathway step 'N-acetylputrescine from putrescine' (which the human gene review keeps as a non-core role). With direct substrate-specificity data negative and the positive claim indirect, the evidence neither validates nor refutes a role of SAT1 in putrescine catabolism.

Supporting Evidence:

file:human/SAT1/SAT1-uniprot.txt: "norspermidine = spermidine >> spermine"
PMID:6615454: "but was inactive with putrescine, cadaverine, sym-homospermidine and N1-acetylspermidine"
PMID:42206375: "Metabolomic analysis identified the microbial conversion of BPF to N-acetylputrescine (NAP). Mechanistically, we found that BPF stimulated intestinal epithelial cells to secrete spermidine/spermine N1-acetyltransferase 1 (Sat1), which catalyzed this conversion"
PMID:1985966: "rate-limiting enzyme in the catabolism of polyamines"

📚 Additional Documentation

Bioinformatics Results

(RESULTS.md)

SAT1: donkey-human sequence comparison

Script: align_to_human.py (Biopython PairwiseAligner, global, BLOSUM62, gap open -10, extend -0.5; with per-50-residue identity windows).
Command: uv run python align_to_human.py ../SAT1-uniprot.txt ../../../human/SAT1/SAT1-uniprot.txt 27 28 92 140 152
Raw output: alignment_output.txt.

Results

The donkey sequence A0A9L0KCT9 (171 residues) aligns to human P21673 (171 residues) with 97.08% identity across 171 paired residues, without gaps.
The human catalytic Tyr140 is conserved (donkey Tyr140), as are the substrate/acetyl-CoA binding residues checked (Tyr27, Glu28, Glu92, Glu152).

Interpretation

The donkey protein is a full-length SAT1 (SSAT1) ortholog with the catalytic machinery intact.

SAT1

Gene Description

Existing Annotations Review

Core Functions

Cytosolic spermidine/spermine N1-acetyltransferase that uses acetyl-CoA to N1-acetylate spermidine and spermine, the rate-limiting step of polyamine catabolism and back-conversion.

References

Suggested Questions for Experts

Suggested Experiments

External Prediction Reviews

ProtNLM2 External predictions

Deep Research

Cyberian

📚 Additional Documentation

Notes

Bioinformatics Results

SAT1: donkey-human sequence comparison

Results

Interpretation

📄 View Raw YAML