Porcine Liver Aminopeptidase B

• Published in: Journal of biochemistry (Tokyo) Vol. 88; no. 6; pp. 1601 - 1605
• Main Authors: KAWATA, Shuji, TAKAYAMA, Shuji, NINOMIYA, Kazuto, MAKISUMI, Satoru
• Format: Journal Article
• Language: English
• Published: Oxford University Press 01.10.1980
• ISSN: 0021-924X; 1756-2651
• DOI: 10.1093/oxfordjournals.jbchem.a133135

Porcine liver aminopeptidase B [EC 3.4.11.6] is highly specific for hydrolysis of β-naphthyl-amides of basic L-amino acids; the Km values for L-arginine β-naphthylamide and L-lyslneβ-naphthylamide were 0.035 and 0.12 mM, respectively. The enzyme was inhibited by various α-amino acids. Among basic amino acids, L-homoarglnme and L-argmlne were the most potent inhibitors, L-lysine and L-norargmme (α-amino-γ-guanidinobutyric acid) being less inhibitory. Hydrophobic amino acids also inhibited the enzyme competitively. This suggests that there is a hydrophobic region that binds the side chain of the substrates or inhibitors in the specificity site of the enzyme. Studies on the inhibitions by L-arglnme derivatives showed that blocking of the α-carboxyl or the a-amino group reduced the inhibitory effect of L-argnne. Porcine liver aminopeptidase B was not inhibited by puromycin, whereas bestatin inhibited the enzyme competitively with a K1 value of 1.4×10-8 M.This enzyme had no kinin-converting activity.