| Abstract: | Extracellular carboxypeptidase was isolated from culture filtrates of Str. spheroides strain 35, using affinity chromatography on bacitracin-silochrome, bacitracin-Sepharose and CABS-Sepharose. The electrophoretically homogenous enzyme was obtained with a 44% yield and 4160-fold purification. The enzyme-molecular weight is 33,000 Da; pI is 4.7. The amino acid composition of carboxypeptidase is as follows: Asp43, Thr30, Ser35, Glu33, Pro30, Gly47-50, Ala38, 1/2 Cys5-6, Val16, Met2, Ile11, Leu15, Tyr8, Phe10, Lys10, His6, Arg9. The enzyme shows an activity optimum at pH 7.5 is stable at pH 6-8, is completely inhibited with EDTA and can be reactivated by Ca2+. The carboxypeptidase from Str. spheroides strain 35 has a dual substrate specificity, i. e., it splits N-substituted di-, three- and tetrapeptides having both neutral and basic amino acids at the C-ends similar to mammalian carboxypeptidases A and B. The enzyme belongs to the family of metallocarboxypeptidases; its properties are very similar to those of carboxypeptidase S from Str. griseus K-1 and of carboxypeptidase T from Thermoactinomyces sp. |
