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    A study for determining mechanism of subtilisin-casein interaction by using inhibition kinetics data
    (Mbr Press Inc, 1998) Aytekin, C; Baysal, ZK
    Casein is a non-specific substrate for the an extacellular protease subtilisin. In this study tyrosine, tryptophan, cysteine, phenol and ethyl-methane sulfonate (EMS) were added to the enzyme-substrate medium in appropriate concentrations to investigate their kinetics effect. The additions of these compounds to incubation medium were found cause to different kinds of inhibitions. The inhibition effects of tyrosine, tryptophan and phenol indicate that the enzyme attacks the aromatic amino acid residues on the substrate. Because the sulfhydryl group of cysteine is a very strong induce protonates the imidazol groups of histidine on the enzyme. This can be explained as cysteine effected that the histidine residues decrease the nucleophilicity of the serine residues in the active site of enzyme. On the other hand the effect of mutagenic compound EMS caused to competitive inhibition. It was observed that this result to be in contradiction with alkylation reagents effect that cause to irreversible inhibition.