Purification and Characterization of an X-Prolyl Dipeptidyl Aminopeptidase from Lactobacillus delbrueckii ssp. bulgaricus LBU-147

¹ Nutritional Science Laboratory, Morinaga Milk Industry Co., Ltd., 1-83, 5-Chome, Higashihara, Zama-City, Kanagawa-Pref., Japan 228

An X-prolyl dipeptidyl aminopeptidase that hydrolyzed L-glycyl-L-prolyl-p-nitroanilide was purified from cells of Lactobacillus delbrueckii ssp. bulgaricus LBU-147 and characterized. The purified enzyme was homogeneous in electrophoresis analysis and appeared to be a trimer because the molecular weight was 270,000 by gel filtration and 90,000 by SDS-PAGE. The optimal pH and temperature for activity were 6.5 and 50°C, respectively. The enzyme was strongly inhibited by metal ions and chemical reagents such as Hg²⁺, Cu²⁺, Fe³⁺ Fe²⁺, diisopropyl fluorophosphate, and p-chloromercuribenzoic acid, but it was weakly activated by sulfhydryl-group protective reagents such as 2-mercaptoethanol, dithiothreitol, and cysteine. These results indicated that this enzyme is a serine protease having its active site near a sulfhydryl group.

Key Words: Lactobacillus delbrueckii ssp. bulgaricus • X-prolyl dipeptidyl aminopeptidase, yogurt

Submitted on December 11, 1990
Accepted on February 26, 1991

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