Purification and Properties of a Dipeptidase fromStreptococcus cremoris

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Abstract
A dipeptidase capable of hydrolyzing l-Leu-Gly was purified from the extract of Streptococcus cremoris H 61 by a method that included ammonium sulfate fractionation, DEAE-cellulose chromatography, hydroxylapatite chromatography, rechromatography on hydroxylapatite and rechromatography on DEAE-cellulose. The purified enzyme exhibited homogeneity in disc electrophoresis. The molecular weight of the enzyme was estimated to be 100,000 by Sephadex G-150 gel filtration. The enzyme exhibited optimum pH at 8.0 and was stable up to 50°C. It was activated by Co2+ and inhibited by EDTA, 1,10-phenanthroline and bestatin. The Km value for l-Leu-Gly was estimated to be 5.0 mm. The enzyme showed a wide range of specificity on dipeptides but hardly hydrolyzed tripeptides.