Acid (Asp/Glu) proteases

Aspartate proteases in viruses act in the processing of polyproteins whereas glutamic proteases are involved in virion maturation. They are a type of enzyme that catalyze the hydrolysis of peptide bonds and use a aspartate or glutamic residue in their active site.

(Wikipedia)

Enzymatic reaction:

Asp-endopeptidase EC.3.4.23.-
Glu-endopeptidase EC.3.4.23.-

Mechanism These proteases are characterized by a conserved motif known as a catalytic dyad consisting of two aspartic acid residues or one glutamic and one aspartic acid residues. One carboxylate groups of these two acid residues assist in proton transfers from a water molecule that acts as the nucleophile, to attack the peptide bond of the peptide or protein to be cleaved. A well-known example of an aspartate protease is pepsin, which is found in the stomach and plays a crucial role in the digestion of proteins.

Genome	Order	Family	Function	Type	MEROPS family	Distribution (low incidence)	Clan (fold)	Interpro	UniProt exemplar
RtRNA	Ortervirales	Retroviridae, Orthoretrovirinae	Virion maturation	Aspartyl	Peptidase A2	Virus, (animals, plant, fungi, protozoa)	AA (pepsin fold)	IPR001969	Gag polyprotein
RtRNA	Ortervirales	Retroviridae, Spumaretrovirinae	Virion maturation	Aspartyl	Peptidase A9	Virus, animals, fungi	AA (pepsin fold)	IPR001641	Pro-pol polyprotein
RtRNA	Ortervirales	Caulimoviridae	Virion maturation	Aspartyl	Peptidase A3	Virus, (plant)	AA (pepsin fold)	IPR000588	Polyprotein
dsDNA	Caudovirales	Salasmaviridae	Self cleaving, Virion maturation	Glutamine	Peptidase G2	Bacteria, virus	GB	IPR021865	Pre-neck appendage protein
dsDNA	Algavirales	Phycodnaviridae	Self cleaving, Virion maturation	Glutamine	Peptidase G2	Bacteria, virus	GB	IPR021865	Chlorovirus glycoprotein repeat domain-containing protein