eryCIV

UniProt ID: A4F7N3
Organism: Saccharopolyspora erythraea (strain ATCC 11635 / DSM 40517 / JCM 4748 / NBRC 13426 / NCIMB 8594 / NRRL 2338)
Review Status: COMPLETE
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Gene Description

EryCIV is a pyridoxal-5'-phosphate (PLP)-dependent enzyme of the TDP-D-desosamine biosynthetic pathway in Saccharopolyspora erythraea, belonging to the DegT/DnrJ/EryC1 family. It is annotated (UniProt/EMBL, MIBiG) as an NDP-6-deoxyhexose 3,4-dehydratase acting in deoxysugar biosynthesis; the precise PLP-dependent reaction (dehydratase vs aminotransferase) has not been experimentally pinned down in the records available, and the existing GOA carries a family-default transaminase annotation that conflicts with the dehydratase name.

Existing Annotations Review

GO Term Evidence Action Reason
GO:0000271 polysaccharide biosynthetic process
IEA
GO_REF:0000118 		MODIFY
Summary: Incorrect biological process. EryCIV acts in biosynthesis of the aminodeoxysugar D-desosamine (a monosaccharide moiety of erythromycin), not a polysaccharide.
Reason: Wrong process class; replace with GO:1901115 (erythromycin biosynthetic process), to which desosamine biosynthesis contributes.
GO:0008483 transaminase activity
IEA
GO_REF:0000118 		UNDECIDED
Summary: Family-default transaminase activity from the DegT/DnrJ/EryC1 fold. However EryCIV is named an NDP-6-deoxyhexose 3,4-dehydratase (UniProt/EMBL, MIBiG), and the dedicated desosamine aminotransferase of the cluster is EryCI. The two electronic assignments conflict and cannot be resolved from the available records.
Reason: Genuine conflict between the dehydratase name and the family-default transaminase term, with no accessible experimental characterization to adjudicate. The PLP cofactor is not in doubt (see below); the precise reaction is.
GO:0030170 pyridoxal phosphate binding
IEA
GO_REF:0000118 		ACCEPT
Summary: PLP binding; consistent across the family assignment and UniProt keyword.
Reason: Correct cofactor for this PLP-dependent DegT/DnrJ/EryC1-family enzyme.
Supporting Evidence:
file:SACEN/eryCIV/eryCIV-uniprot.txt
EryCIV NDP-6-deoxyhexose 3,4-dehydratase

Core Functions

PLP-dependent DegT/DnrJ/EryC1-family enzyme contributing to TDP-D-desosamine biosynthesis (named as an NDP-6-deoxyhexose 3,4-dehydratase), supplying the aminodeoxysugar used in erythromycin biosynthesis. The precise PLP reaction awaits experimental confirmation, so only the cofactor-binding MF is asserted here (see the EVIDENCE GAP in suggested_questions).

Molecular Function:
pyridoxal phosphate binding
Directly Involved In:
erythromycin biosynthetic process
Supporting Evidence:
  • file:SACEN/eryCIV/eryCIV-uniprot.txt
    EryCIV NDP-6-deoxyhexose 3,4-dehydratase

References

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Suggested Questions for Experts

Q: EVIDENCE GAP: what is the actual PLP-dependent reaction of EryCIV? Its UniProt/EMBL name ("NDP-6-deoxyhexose 3,4-dehydratase") and the GOA term ("transaminase activity") are conflicting electronic (IEA) assignments, and no experimental annotation exists. The dedicated desosamine aminotransferase of the cluster is EryCI, so a second transaminase is unexpected. Tracked in projects/FUNCTION_KNOWLEDGE_GAPS.md.

Suggested Experiments

Experiment: Biochemically reconstitute EryCIV to determine whether it catalyzes a PLP-dependent 3,4- dehydration/isomerization or a transamination on the TDP-keto-deoxysugar precursor, resolving the conflicting electronic annotations.

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