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Purification and characterization of two extracellular proteinases from Arthrobacter nicotianae 9458.

Two extracellular serine proteinases with molecular masses of about 53-55 and 70-72 kDa, were purified from Arthrobacter nicotianae 9458 and characterized. The enzymes differed with respect to temperature optimum, 55-60 and 37 degrees C, respectively, tolerance to low values of pH and temperature, heat stability, sensitivity to EDTA and sulfhydryl blocking agents, and hydrophobicity. Both proteinases were optimally active in the pH range of 9.0 and 9.5, had considerable activity at pH 6.0 on alpha s1- and beta-caseins, and tolerated NaCl over 5%. Specificity on casein fractions was generally similar and beta-casein was more susceptible to hydrolysis than alpha s1-casein. The proteinases of Arthrobacter spp. may play a significant role in ripening of the smear surface-ripened cheeses.