the best p-nitrophenyl ester substrates were benzyloxycarbonyl-tyr p-nitrophenyl ester ( kcat./km 3,536,000 m-1 x s-1 ) , benzyloxycarbonyl-leu p-nitrophenyl ester ( kcat./km 2,250,000 m-1 x s-1 ) and benzyloxycarbonyl-phe p-nitrophenyl ester ( kcat./km 1,000,000 m-1 x s-1 ) consistent with a preference for aliphatic or aromatic amino acids at subsite s1 .
C0031453
phe
C0301713
aromatic amino acids