CG33090

UniProt ID: X2JE45
Organism: Drosophila melanogaster
Review Status: DRAFT
πŸ“ Provide Detailed Feedback

Gene Description

CG33090 is the single Drosophila melanogaster ortholog of the GBA2 non-lysosomal glucosylceramidases, members of glycoside hydrolase family 116 (GH116; PANTHER PTHR12654:SF0). Its 948-residue PB product (Q7KT91) aligns over its catalytic core with human GBA2, which hydrolyzes glucosylceramide to glucose and ceramide using a retaining mechanism with a glutamate nucleophile and an aspartate acid/base. X2JE45 is the 799-residue PC isoform. In PC a distinct 28-residue N terminus replaces PB residues 1-177, the region corresponding to roughly the first 193 residues of human GBA2, which include part of the N-terminal beta-sandwich domain. PC keeps the rest of the N-terminal domain, the complete catalytic region and both catalytic residues (Glu362 and Asp575). The fly gene has not been characterized experimentally. Its glycosidase activity, physiological substrates (for example insect glucosylceramides), subcellular location and physiological role are inferred from GBA2 orthology. Whether the shortened PC isoform is catalytically active is not known.

Existing Annotations Review

GO Term Evidence Action Reason
GO:0004553 hydrolase activity, hydrolyzing O-glycosyl compounds
IEA
GO_REF:0000002 		UNDECIDED
Summary: Plausible family-level glycosidase activity, but unresolved for the exact PC isoform, which lacks the GBA2 N-terminal region corresponding to human residues 1-193.
Reason: The InterPro2GO mapping from the GH116 catalytic region (IPR006775) correctly describes the family chemistry. CG33090 is grounded phylogenetically as the GBA2 ortholog: X2JE45 itself is classified in PANTHER subfamily PTHR12654:SF0, the same subfamily as human GBA2, and it keeps the experimentally defined catalytic nucleophile and acid/base pair (PC Glu362 and Asp575, equivalent to human Glu527 and Asp677). The difficulty is the isoform. The re-review mapping shows that PC's shared sequence begins at human GBA2 position 194, so PC has no counterpart for human residues 1-193. That region includes the N-terminal-domain beta-strand where a six-residue insertion (between human residues 189 and 190, isoform X1) abolished detectable activity even though the protein was expressed. Human isoforms with other internal changes were also inactive. These results do not prove PC inactive, because none of the human variants match the PC truncation, but they remove the usual basis for treating any product with an intact catalytic domain as active. GO usually records function at the gene level, and the longer CG33090 products such as PB/Q7KT91 would be expected to carry beta-glucosidase activity from the GBA2 subfamily. For this accession, neither activity nor inactivity is established. The row stays UNDECIDED and should not be refined to beta-glucosidase or glucosylceramidase activity until the native PC protein is assayed.
Supporting Evidence:
file:DROME/CG33090/CG33090-uniprot.txt
DR PANTHER; PTHR12654:SF0; NON-LYSOSOMAL GLUCOSYLCERAMIDASE; 1.
file:DROME/CG33090/CG33090-bioinformatics/RESULTS.md
Both global and local MAFFT alignments map human GBA2 Glu527 to PC Glu362 and Asp677 to PC Asp575 (PB Glu511 and Asp724). The catalytic nucleophile and acid/base residue types are retained.
file:DROME/CG33090/CG33090-bioinformatics/RESULTS.md
PC has a distinct 28-residue N-terminus followed by a 771-residue sequence identical to PB residues 178–948.
file:DROME/CG33090/CG33090-bioinformatics/RESULTS-rereview.md
In both alignments PC position 29, the first residue of the sequence shared with PB, aligns with PB position 178 and human GBA2 position 194.
PMID:33261081
Surprisingly, isoform X1, which has an insertion of six amino acid between residues 189 and 190 in a Ξ²-strand of the N-terminal non-catalytic domain compared to isoform 1, showed no significant activity, indicating that the structural integrity of the N-terminal domain is also critical to the activity.
PMID:33261081
Thus, all human GBA2 isoforms were expressed but only isoform 1 clearly hydrolyzed the MUG substrate.
GO:0005975 carbohydrate metabolic process
IEA
GO_REF:0000002 		MARK AS OVER ANNOTATED
Summary: A generic six-hairpin glycosidase superfamily mapping. It does not describe the GBA2 subfamily process, and activity of the PC isoform is unproven.
Reason: The row is propagated from the six-hairpin glycosidase superfamily signatures (IPR008928, IPR012341). These are shared by many carbohydrate-active enzyme families with unrelated substrates, so the term carries no information about the GBA2 subfamily. GBA2 family chemistry acts on glucosylceramide, a glycosphingolipid. In GO, glucosylceramide catabolic process falls under lipid metabolic process and carbohydrate derivative metabolic process, not under carbohydrate metabolic process, so the term does not fit the expected biology even for the full-length CG33090 products. For this PC isoform, any catalytic process participation also depends on the unresolved activity question raised for the glycosidase row. No specific replacement is proposed: the more specific candidate, glucosylceramide catabolic process, has not been shown for any Drosophila product, and PAINT has not propagated it to this gene.
Supporting Evidence:
file:DROME/CG33090/CG33090-bioinformatics/RESULTS.md
PC has a distinct 28-residue N-terminus followed by a 771-residue sequence identical to PB residues 178–948.
file:DROME/CG33090/CG33090-bioinformatics/RESULTS-rereview.md
In both alignments PC position 29, the first residue of the sequence shared with PB, aligns with PB position 178 and human GBA2 position 194.
PMID:33261081
Surprisingly, isoform X1, which has an insertion of six amino acid between residues 189 and 190 in a Ξ²-strand of the N-terminal non-catalytic domain compared to isoform 1, showed no significant activity, indicating that the structural integrity of the N-terminal domain is also critical to the activity.

Core Functions

Predicted GH116 retaining beta-glucosidase, inferred for the CG33090 gene from its 1:1 orthology to human GBA2 within PANTHER subfamily PTHR12654:SF0 and from conservation of the catalytic nucleophile/acid-base pair. The physiological substrate in the fly (by analogy with GBA2, glucosylceramide) and the subcellular site of action have not been tested. This entry describes the gene-level expectation for its full-length products. Whether the N-terminally truncated PC isoform (X2JE45) shares the activity is unresolved, which is why the corresponding existing annotation is UNDECIDED.

Molecular Function:
beta-glucosidase activity
Supporting Evidence:
  • file:DROME/CG33090/CG33090-uniprot.txt
    DR PANTHER; PTHR12654:SF0; NON-LYSOSOMAL GLUCOSYLCERAMIDASE; 1.
  • file:DROME/CG33090/CG33090-bioinformatics/RESULTS.md
    Both global and local MAFFT alignments map human GBA2 Glu527 to PC Glu362 and Asp677 to PC Asp575 (PB Glu511 and Asp724). The catalytic nucleophile and acid/base residue types are retained.
  • file:DROME/CG33090/CG33090-bioinformatics/RESULTS-rereview.md
    In both alignments PC position 29, the first residue of the sequence shared with PB, aligns with PB position 178 and human GBA2 position 194.

References

Loading supporting content…

Download this section (compressed HTML)

Suggested Questions for Experts

Q: Is the CG33090-RC transcript, which encodes the N-terminally truncated PC isoform, translated at appreciable levels in any tissue, and does its product retain the activity of the full-length GBA2 ortholog?

Q: Do CG33090 loss-of-function flies accumulate glucosylceramide or other glucosylated lipids, as GBA2-deficient mammals do?

Suggested Experiments

Experiment: Express FLAG-tagged CG33090-PB and CG33090-PC side by side in Drosophila S2 cells (or COS-7 cells, as for the human isoforms) and measure 4-methylumbelliferyl beta-D-glucoside hydrolysis and glucosylceramide turnover with conduritol-B-epoxide-insensitive assays, including PB E511A and D724A catalytic mutants as negative controls.

Experiment: Profile glucosylceramides and ceramides in CG33090 null or RNAi flies versus controls, with transgenic rescue by PB or PC, to establish the in vivo substrate and test each isoform's contribution.

Knowledge Gaps

What is not known β€” curated, literature-grounded statements of the open unknowns (the inverse of core functions).

Gap: It is unknown whether the CG33090-PC isoform, which lacks the region corresponding to human GBA2 residues 1-193, folds into an active GH116 glucosidase, and whether any CG33090 product hydrolyzes glucosylceramide in the fly.

OPEN BIOLOGY

What is known: The longer CG33090 products are GBA2 orthologs with intact catalytic residues. PC keeps the catalytic region but has a different N terminus. Human GBA2 isoforms with smaller N-terminal-domain changes were inactive. No Drosophila CG33090 product has been assayed.

What would resolve it: Isoform-resolved expression and activity assays of PC versus PB, plus lipidomics of CG33090 mutant flies.

Provenance (the field's own admissions):

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 Β· CG33090-protnlm-predictions-review.yaml Β· Review status: COMPLETE

Hydrolase activity is plausible from the conserved GBA2 catalytic core, but remains unresolved for the distinct native PC N-terminal architecture.

Source documents: projects/PROTNLM_EVALUATION/fly-benchmark/predictions.jsonl.gz Β· genes/DROME/CG33090/CG33090-predictions-source.json

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

GO:0004553 hydrolase activity, hydrolyzing O-glycosyl compounds GO_MF
UNC β€” Uncertain Review score: 1/2
Prediction method: ProtNLM2 Β· Version: UniProt API snapshot 2026-09-08
Review rationale: X2JE45 is the native 799-residue PC isoform. It retains the catalytic residues corresponding to human GBA2 Glu527 and Asp677, but replaces PB residues 1–177 with a distinct 28-residue N-terminus that alters the GH116 N-terminal region. Human GBA2 isoform experiments establish that such noncatalytic-domain changes can impair activity; they do not demonstrate that this different fly isoform is inactive. The specific missing evidence is activity or fold integrity of native PC, rather than uncertainty about the GBA2 family as a whole. The term is not novel, because X2JE45 already carries it by InterPro2GO IEA and the gene's PB product (Q7KT91) carries the more specific beta-glucosidase activity (GO:0008422) by IBA; the gene review leaves the X2JE45 row UNDECIDED for the same isoform reason. No experimental study of CG33090 or of any Drosophila GBA2 product was found in PubMed.
Supporting Evidence:

Deep Research

Falcon

(CG33090-deep-research-falcon.md)

Loading supporting content…

Download this section (compressed HTML)

πŸ“š Additional Documentation

Notes

(CG33090-notes.md)

Loading supporting content…

Download this section (compressed HTML)

Bioinformatics Results

(RESULTS.md)

Loading supporting content…

Download this section (compressed HTML)

πŸ“„ View Raw YAML

Loading supporting content…

Download this section (compressed HTML)