GPI-anchor transamidase activity (GO:0003923) issues

[ValWood]

GPI8/PIG-K

GPI-anchor transamidase activity (GO:0003923)
Definition
Catalysis of the formation of the linkage between a protein and a glycosylphosphatidylinositol anchor. The reaction probably occurs by subjecting a peptide bond to nucleophilic attack by the amino group of ethanolamine-GPI, transferring the protein from a signal peptide to the GPI anchor.

"Catalysis of the formation of the linkage between a protein and a glycosylphosphatidylinositol anchor"
is describing a transferase activity, but this term is a subclass of
cysteine-type endopeptidase activity

In reality this enzyme appears to have 2 activities, i) cleaving the signal peptide, and ii) transferring the GPI anchor onto the protein

[deustp01]

In reality this enzyme appears to have 2 activities, i) cleaving the signal peptide, and ii) transferring the GPI anchor onto the protein

I din't know any actual data here, but there is the textbook possibility that this is a transpeptidation in which the cleavage and transfer are accomplished in a single reaction.

[ValWood]

That appears the case
see figure 3
https://www.researchgate.net/publication/6446252_Thematic_review_series_Lipid_Posttranslational_Modifications_GPI_anchoring_of_protein_in_yeast_and_mammalian_cells_or_how_we_learned_to_stop_worrying_and_love_glycophospholipids/figures?lo=1

In this situation I guess we add the missing parent
GO:0008483 transaminase activity to the MF GO:0003923 GPI-anchor transamidase activity

and keep the cysteine-type endopeptidase.

[ValWood]

whoops that is GO:0008483 transaminase activity we don't have " transamidase activity"

facilitates the transfer of an amide group (-CONH2) from one molecule to another.
General reaction:

R-CONH-R’ + R”-NH2 → R-CO-NH-R” + R’-NH2 R-CONH-R’+R”-NH2→R-CO-NH-R”+R’-NH2

[ValWood]

@pgaudet we do not have " transamidase activity" so I will add the parent
GO:0016769 transferase activity, transferring nitrogenous groups

I

[ValWood]

another bit of weirdness.

This has an additional redundant parent in Protege?
"catalytic activity acting on a protein"

:

Why is that?

[pgaudet]

another bit of weirdness.
This has an additional redundant parent in Protege?
"catalytic activity acting on a protein"

What's wrong with this?

[ValWood]

I wasn't sure why it has the instantiated subclass of a parent term?
"catalytic activity, acting on a protein"
But it doesn't show in QuickGO as a relationship