The effect of thermal treatment on the catalytic activity and biological properties of Bacillus intermedius ribonuclease

Bacillus intermedius ribonuclease (binase), which is known to exert a growt h-stimulating effect at low concentrations and a genotoxic effect at high c oncentrations, loses these abilities completely after exposure to 100 degre esC for 10 min, but retains approximately 95% of its catalytic activity and structural integrity. Other types of modification, such as photoinactivati on and site-specific mutagenesis, gave rise to enzyme forms with unaltered structure but reduced (sometimes to trace amounts) catalytic activity. Geno toxicity was always proportional to the catalytic activity of the native en zyme, while a notable growth-stimulating effect could be exerted by enzymes with low activity. The loss of biological activity of thermoinactivated bi nase was related to the increase in the number of negatively charged groups on the enzyme surface, which led to a substantial decline in the adhesive properties of the enzyme.