Purification and characterization of two extracellular proteinases from Arthrobacter nicotianae 9458

Two extracellular serine proteinases with molecular masses of about 53-55 a nd 70-72 kDa, were purified from Arthrobacter nicotianae 9458 and character ized. The enzymes differed with respect to temperature optimum. 55-60 and 3 7 degrees C, respectively, tolerance to low values of pH and temperature, h eat stability, sensitivity to EDTA and sulfhydryl blocking agents, and hydr ophobicity. Both proteinases were optimally active in the pH range of 9.0 a nd 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)-c asein. The proteinases of Arthrobacter spp. may play a significant role in ripening of the smear surface-ripened cheeses. (C) 1999 Federation of Europ ean Microbiological Societies. Published by Elsevier Science B.V. an rights reserved.