Аннотация:Carboxypeptidase Т (CPТ) from Thermoactinomyces vulgaris has folding and active site composition similar to that of carboxypeptidase B( CPB) specific to positively charged substrates but unlike CPB is able to cleave as positively charged as hydrophobic residues from C-end of peptides. To elucidate structure basis of the double substrate selectivity of CPT crystal structures if complexes of CPT with the transition state stable analogs, N-sulfamoyl-L-phenylalnine and N-sulfamoyl-L-arginine with the resolution of 1.55 Å and 1.39 Å correspondingly were received. Substrate-dependent changes in active site loop Pro248-Asp258 was found. It was shown also that transition state complex with N-sulfamoylphenylalanine is similar to the base state complex with benzenesuccinic acid. In contrast, complex with arginine analogs has different conformation of the side chain of ligands in the basic and transition state and catalytic center groups. The fact that CPT structure is more complimentary to the transition state of phenylalanine substrates hydrolysis than to arginine transition state may explain reduced effectivity of arginine substrates catalysis in comparison with hydrophobic ones despite similarity of CPT and CPB active sites.