Gene Ontology annotation through association of InterPro records with GO terms

Manual transfer of experimentally-verified manual GO annotation data to orthologs by curator judgment of sequence similarity

GO_REF:0000041

Gene Ontology annotation based on UniPathway vocabulary mapping

GO_REF:0000044

Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location vocabulary mapping, accompanied by conservative changes to GO terms applied by UniProt

GO_REF:0000120

Combined Automated Annotation using Multiple IEA Methods

file:DANRE/gpat3/gpat3-uniprot.txt

UniProtKB entry Q6DG38 for Danio rerio gpat3

ER-membrane acyltransferase forming LPA from G3P (by similarity to human Q53EU6).

"by incorporating an acyl moiety at the sn-1 position of the glycerol backbone"

file:DANRE/gpat3/gpat3-deep-research-falcon.md

Falcon deep research report on zebrafish gpat3 (Q6DG38)

The best-supported molecular function for zebrafish gpat3 is an acyl-CoA-dependent lysophosphatidic acid acyltransferase (AGPAT/LPAAT) activity, inferred from the human ortholog AGPAT10/GPAT3, which directly catalyzes LPA + acyl-CoA to phosphatidic acid (PA).

"zebrafish **gpat3 (Q6DG38)** encodes an ER/microsome-associated acyltransferase in the GPAT/AGPAT superfamily that likely participates in **PA production** for glycerolipid synthesis. The strongest direct enzymology in the retrieved corpus comes from the human ortholog labeled **AGPAT10/GPAT3**, which catalyzes **LPA + acyl-CoA → PA + CoA**"
Substrate specificity (ortholog-based): activity is strongest with 1-oleoyl-LPA as the acyl acceptor and oleoyl-CoA (C18:1) as the acyl donor, with strong selectivity for the LPA headgroup over other lysophospholipids (LPS, LPC, LPE, LPG, LPI).

"activity was strongest with **1-oleoyl-LPA** as acyl acceptor and **oleoyl-CoA (C18:1)** as acyl donor. Several alternative LPA acceptors (e.g., C16:0, C18:3, C20:4) produced ~50% lower activity than 1-oleoyl-LPA in the reported assays"
Subcellular localization is the endoplasmic reticulum: the human AGPAT10/GPAT3-GFP fusion shows an ER-like pattern and colocalizes with the ER marker Sec61-beta; zebrafish ER localization is inferred from ortholog/family evidence.

"an AGPAT10/GPAT3-GFP fusion displayed an ER-like pattern and colocalized with an ER marker (Sec61-β), and AGPAT9-family GFP fusions colocalized with multiple ER markers and with AGPAT1 in CHO cells"
Nomenclature caveat: some isoforms historically labeled GPAT3 behave primarily as AGPAT (LPA acyltransferase) in vitro, producing PA from LPA rather than LPA from G3P, with no detectable GPAT activity in the assay system tested. This underlies the dual EC (2.3.1.15 / 2.3.1.51) and GPAT3-vs-AGPAT10 naming for Q6DG38.

"some isoforms historically labeled “GPAT3” have been experimentally observed to behave primarily as **AGPAT (LPA acyltransferase)** under certain assay systems, producing PA from LPA rather than producing LPA from G3P; this is the basis of the AGPAT10/GPAT3 dual naming"
The GPAT/AGPAT family shares conserved acyltransferase motifs, including the catalytic HXXXXD motif, supporting domain-level functional inference for zebrafish gpat3 (UniProt lists Plipid/glycerol_acylTrfase / PF01553 and LPCAT1-like features).

"GPAT/AGPAT-family enzymes share conserved acyltransferase sequence motifs, including the catalytic **HXXXXD** motif, and additional motifs involved in acceptor/donor recognition"
Phosphatidic acid produced by this pathway is a central intermediate for triacylglycerol (TAG) and glycerophospholipid synthesis, consistent with the triglyceride and CDP-diacylglycerol biosynthetic process annotations.

"PA is a central intermediate for synthesis of **triacylglycerol (TAG)** and glycerophospholipids"
Direct zebrafish evidence is limited to pathway-level/transcriptomic data: in a tango2-deficient zebrafish model of rhabdomyolysis susceptibility, gpat3 expression is normal at baseline but decreases under extrinsic stressors (caffeine or mechanical loading), linking gpat3 to membrane/glycerolipid homeostasis under stress.

"**gpat3 expression is reported as normal at baseline** but shows **decreased expression under extrinsic stressors** (caffeine or mechanical loading)"
Ortholog-based kinetic parameters provide quantitative support: human AGPAT10/GPAT3 activity was about ~2 nmol/min/mg in lysates, with Km(acyl-CoA) 2.7 mM, Vmax 60 nmol/min/mg and Km(LPA) 9.2 mM, Vmax 14.19 nmol/min/mg.

"**Km(acyl-CoA) = 2.7 mM; Vmax = 60 nmol/min/mg** and **Km(LPA) = 9.2 mM; Vmax = 14.19 nmol/min/mg**"

GO_REF:0000033

Annotation inferences using phylogenetic trees

PMID:17170135

Molecular identification of microsomal acyl-CoA:glycerol-3-phosphate acyltransferase, a key enzyme in de novo triacylglycerol synthesis.

GPAT3 overexpression increases NEM-sensitive GPAT activity specifically toward G3P.

"Ectopic expression of GPAT3 leads to a significant increase in N-ethylmaleimide-sensitive GPAT activity, whereas acyltransferase activity toward a variety of other lysophospholipids, as well as neutral lipid substrates, is not altered."
GPAT3 overexpression increases TAG but not phospholipid synthesis.

"Overexpression of GPAT3 in mammalian cells results in increased triacylglycerol, but not phospholipid, formation."
No LPA acyltransferase activity was detected for GPAT3 in this study.

"Importantly, acyltransferase activity conferred by GPAT3 overexpression is specific toward G3P, because no significant increase in product formation was observed when LPA, lysophosphatidylcholine, lysophosphatidylserine, lysophosphatidylglycerol, MAG, or DAG were presented as substrates"
GPAT3 localises to the ER.

"GPAT3 is localized to the ER when overexpressed in COS-7 cells."

PMID:19318427

Functional characterization of the human 1-acylglycerol-3-phosphate-O-acyltransferase isoform 10/glycerol-3-phosphate acyltransferase isoform 3.

Human AGPAT10/GPAT3 shows robust AGPAT activity but no GPAT activity in HEK-293 lysates.

"In vitro enzymatic activity using lysates of human embryonic kidney-293 cells infected with recombinant AGPAT10/GPAT3 adenovirus show that the protein has a robust AGPAT activity with an apparent V(max) of 2 nmol/min per mg protein, but lacks GPAT enzymatic activity."
The protein localises to the ER in CHO cells.

"When this AGPAT10/GPAT3 cDNA was expressed in Chinese Hamster ovary cells, the protein product localizes to the endoplasmic reticulum."
Human AGPAT10/GPAT3 is highly conserved with zebrafish.

"The human AGPAT10/GPAT3 is highly conserved with mouse, zebrafish, Caenorhabditis elegans, and Arabidopsis (Supplementary material)."

PMID:24714397

Mice deleted for GPAT3 have reduced GPAT activity in white adipose tissue and altered energy and cholesterol homeostasis in diet-induced obesity.

Gpat3-/- mice lose 80% of total GPAT activity in white adipose tissue.

"Total GPAT activity in white adipose tissue of Gpat3(-/-) mice was reduced by 80%, suggesting that GPAT3 is the predominant GPAT in this tissue."