Purification and properties of a new psychrophilic metalloprotease (Fpp2) in the fish pathogen Flavobacterium psychrophilum

To go further into the characterization of the proteolysis exocellular system of the salmonid pathogen Flavobacterium psychrophilum, the purification and characterization of a novel protease designated Fpp2 (F. psychrophilum protease 2) was undertaken. A protease (Fpp2) hydrolyzing azocasein was purified. The Fpp2 can be defined as a metalloprotease, it had an estimated molecular mass of 62 kDa with calcium playing an important role in the thermostability of the enzyme. Proteolytic activity was optimal at pH 6.0-7.0 and 24degreesC and activation energy for the hydrolysis of azocasein was determined to be 5.4 kcal mol(-1), being inactive at temperatures above 42degreesC. All these results are characteristic of 'cold adapted enzymes'. Fpp2 proved to be a broad range hydrolytic enzyme because in optimal conditions it was able to hydrolyze matrix and muscular proteins. It can be concluded that the Fpp1, a previously characterized 55 kDa metalloprotease, and the Fpp2 protease were produced under different physiological conditions and were immunologically as well as biochemically different. (C) 2003 Federation of European Microbiological Societies. Published by Elsevier B.V. All rights reserved.