Purification and characterization of aminopeptidase B from Escherichia coli K-12.
Aminopeptidase B, which is one of the four cysteinylglycinases of Escherichia coli K-12, was purified to electrophoretic homogeneity and its enzymatic characteristics were observed. Aminopeptidase B was activated by various divalent cations such as Ni2+, Mn2+, Co2+, and Cd2+, and lost its activity completely on dialysis against EDTA. This indicates that aminopeptidsase B is a metallopeptidase. It was stabilized against heat in the presence of Mn2+ or Co2+. The activity of aminopeptidase B, which was saturated with one of above divalent cations, was enhanced on the addition of a very small amount of a second divalent cation. Alpha-glutamyl p-nitroanilide, leucine p-nitroanilide, and methionine p-nitroanilide were good substrates for aminopeptidase B, while native peptides, cysteinylglycine and leucylglycine, were far better substrates. The kcat/Km for cysteinylglycine was much bigger than those for leucylglycine or leucine p-nitroanilide.
Suzuki
H
H
Division of Integrated Life Science, Graduate School of Biostudies, Kyoto University, Japan. hideyuki@lif.kyoto-u.ac.jp
Kamatani
S
S
Kumagai
H
H
D000626:Aminopeptidases / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D001483:Base Sequence; D002413:Cations, Divalent / Q000494:pharmacology; D004269:DNA, Bacterial / Q000235:genetics; D004492:Edetic Acid / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D004795:Enzyme Stability / Q000187:drug effects; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D005798:Genes, Bacterial; D006358:Hot Temperature; D007700:Kinetics; D012492:Salts / Q000494:pharmacology; D013379:Substrate Specificity
D002413:Cations, Divalent; D004269:DNA, Bacterial; D012492:Salts; D004492:Edetic Acid; D000626:Aminopeptidases; C019721:aminopeptidase B