Table 1.

Preliminary BRENDA-supplied entries of aspartic proteinases

EC-class	Name	Reaction and specificity
3.4.23.B6	Mason-Pfizer monkey virus proteinase	The enzyme cleaves 17 amino acids of the C-terminal 38-amino-acid cytoplasmic tail of the transmembrane protein TM of the released immature virus.
3.4.23.B10	Rous sarcoma virus retropepsin	The cleavage sequence in the natural substrate NC-PR is PPAVS-/-LAMTMRR. The activity can be improved by substitution by Trp, Tyr, Phe, Leu, Arg, Glu, His or Ala in P1, Tyr in P3′, and Arg, Phe, Asn or His in P3.
3.4.23.B11	Spumapepsin	Good cleavage at the peptide bonds: Asn-Thr, Asn-Gln, Asn-Cys and Asn-Ala.
3.4.23.B13	Proteinase P15	Efficient cleavage of Ala-Thr-His-Glu-Val-Tyr-Phe(NO2)-Val-Arg-Lys-Ala, no cleavage with Ser, Arg or Glu at P1, Gly or Phe at P2, and Pro at P3. Specifically liberates the five major structural proteins from the common gag precursor, as well as reverse transcriptase and integrase from the gag-pol precursor.
3.4.23.B14	Plasmepsin IV	Cleavage of hemoglobin. In the S3 and S2 subsites, the plasmepsin 4 orthologs all prefer hydrophobic amino acid residues, Phe or Ile, but reject charged residues such as Lys or Asp. In S2′ and S3′ subsites these plasmepsins tolerate both hydrophobic and hydrophilic residues.
3.4.23.B2	Simian immunodeficiency virus proteinase	The enzyme may have a wide substrate specificity. Good cleavage of the peptide bonds Met-Met and Tyr-Pro. Cleavage is also observed at Phe-Pro, Phe-Leu, Leu-Phe, Leu-Ala, Glu-Ala and Tyr-Ala.
3.4.23.B3	Equine infectious anemia virus proteinase	Processing at the authentic HIV-1 PR recognition site and release of the mature p17 matrix and the p24 capsid protein, as a result of the cleavage of the -SQNY-/-PIVQ- cleavage site.
3.4.23.B4	Feline immunodeficiency virus protease	The enzyme seems to have a preference for Val in P1′ and Phe in P1. In contrast to the HIV-1 protease the feline immunodeficiency virus protease does not cleave the peptide KSGVFVQNGLVK at the Phe-Val bond. Gln in P2′ may be inhibitory. In contrast to HIV-1 protease the feline immunodeficiency virus protease does not cleave peptide KSGNFVVNGLVK at the Phe-Val bond. Asn in P2 may be inhibitory.
3.4.23.B5	Murine leukemia virus protease	Processing of viral polyprotein. The retroviral protease is essential for virus replication, by processing of viral Gag and Gag-Pol polyproteins.
3.4.23.B8	Human T-cell leukemia virus type 1 protease	Processing at the authentic HIV-1 PR recognition site and release of the mature p17 matrix and the p24 capsid protein, as a result of the cleavage of the -SQNY-/-PIVQ- cleavage site.
3.4.23.B9	Bovine leukemia virus protease	The best substrate YDPPAILPII is bearing the natural cleavage site between the matrix and the capsid proteins of BLV Gag precursor. polyprotein. Good cleavage of the peptide bonds: Leu-Pro, Leu-Val, Gly-Val and Leu-Pro.
3.4.23.B1	Napsin	proteolytic cleavage of polypeptides to large and stable peptides.
3.4.23.B17	Walleye dermal sarcoma virus proteinase	Processing of viral polyprotein. Preference order for P1 position is Phe > Tyr > Leu, Met > Ala. Gly is preferred at position P3. Ala and Pro are preferred at position P4. Asn, Cys or Leu are preferred at position P2.
3.4.23.B18	Mouse mammary tumor virus retropepsin	Processing of viral polyprotein. Selective for large aromatic residues (Tyr and Phe) at position P1. Phe and Leu are preferred at position P3. No hydrolysis of substrates with Gly or Ala at position P3. Medium-sized or large hydrophobic residues as Ile, Leu and Phe are preferred at position P4.
3.4.23.B19	Plasmepsin V	Cleavage of hemoglobin. In contrast to the food vacuole plasmepsins, detergent-solubilized PMV does not bind the aspartic protease inhibitor pepstatin.
3.4.23.B20	HycD peptidase	This enzyme specifically removes a 15-amino acid peptide from the C-terminus of the precursor of the large subunit of hydrogenase 2 [UniProt: P0ACE0] in E. coli.