Diphenolases from Anoxybacillus kestanbolensis strains K1 and K4 T , highly active against 4-methylcatechol were characterized in terms of pH-and temperature-optima, pH-and temperature-stability, kinetic parameters, and inhibition/activation behaviour towards some general polyphenol oxidase (PPO) inhibitors and metal ions. The temperature-activity optima, for Anoxybacillus kestanbolensis K1 and K4 T catecholases in the presence of 4-methylcatechol, were 80 and 70°C, respectively. Although catecholase from A. kestanbolensis K4 T lost no activity after a period of 1 h incubation at its optimum temperature, the enzyme from K1 was stimulated by keeping at 80°C. Both of the enzymes possessed pH optima at 9.5, and the pH-stability profiles showed that cathecholases from both preparations retained their activities at alkaline pH values. Both A. kestanbolensis K1 and K4 T catecholase activities were totally inhibited by addition of 0.01 mM sodium metabisulphite, ascorbic acid and L -cysteine. 1 mM Mn 2+ increased the activities of A. kestanbolensis K1 and K4 T catecholases by 6.4-and 5.3-fold, respectively. These results indicate that both A. kestanbolensis K1 and K4 T strains possess thermo-and alkalostable catecholases.
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