Family A9

Family

Summary Holotypes Alignment Tree Genomes Structure Literature Architecture

Summary for family A9

Name	Peptidase family A9 (spumapepsin family)
Family type peptidase	A09.001 - spumapepsin (human spumaretrovirus), MEROPS Accession MER0001439 (peptidase unit: 14-180)
Content of family	Peptidase family A9 contains an endopeptidase, spumapepsin.
History	Identifier created: Proteolysis in Cell Function, pp13-21, IOS Press, Amsterdam (1997)
Catalytic type	Aspartic
Active site residues	D24
Active site	The active site Asp of spumapepsin has been identified by site-directed mutagenesis (Konvalinka et al., 1995), and like other viral endopeptidases in clan AA, spumapepsin is assumed to be active only as a dimer with one Asp from each monomer forming the active site dyad. The active site Asp occurs in a Asp-Xaa-Gly motif where Xaa is Ser or Thr. No sequence equivalent to the pepsin (A01.001) 'flap' has been identified.
Activities and specificities	Spumapepsin processes both the Gag and Pol viral polyproteins. Four cleavages are made, all except one being at asparaginyl bonds. Spumapepsin has also been shown to cleave Pol polyproteins of the yeast Ty1 and Ty3 retrotransposons (Fenyofalvi et al., 1999). Cleavage occurs at neutral pH.
Inhibitors	No inhibitors have been reported.
Molecular structure	The tertiary structure of spumapepsin has not been determined. In human foamy virus, spumapepsin is part of the Gag polyprotein, but in simian foamy virus it is part of the Pol polyprotein (Renne et al., 1992). The presence of the motif Asp-Ser/Thr-Gly around the active site Asp in both spumapepsin and pepsin, the type example of clan AA, is the basis for the inclusion of family A9 in clan AA.
Clan	AA
Basis of clan assignment	Active site residues for members of this family and family A1 occur in the motif D-T/S-G.

Distribution of family	Bacteria	-
	Archaea	-
	Protozoa	-
	Fungi	-
	Plants	details
	Animals	details
	Viruses	details

Biological functions	Processing of the Gag polyprotein by spumapepsin is essential for viral infectivity: without it viral cDNA is not synthesized (Enssle et al., 1997). The Pol polyprotein is processed to release the reverse transcriptase and the integrase.
Statistics for family A9	Sequences:	28
	Identifiers:	1
	Identifiers with PDB entries:	1
Downloadable files	Sequence library (FastA format)
	Sequence alignment (FastA format)
	Phylogenetic tree (Newick format)

Other databases	INTERPRO	IPR001641
	PFAM	PF03539

Peptidases and Homologues	MEROPS ID	Structure
spumapepsin	A09.001	Yes
Family A09 unassigned peptidases	unassigned	-