Relationship between the Hydrophobicity of Dipeptides and the Michaelis–Menten Constant Km of Their Hydrolysis by Carboxypeptidase-Y and Carboxypeptidase-A

Abstract The enzymatic hydrolysis of dipeptides by carboxypeptidase-Y and carboxypeptidase-A was investigated. In the enzymatic hydrolysis of the dipeptides, a good linear relationship (r = 0.997 and 0.999) was found between the Michaelis–Menten constant (Km) and the hydrophobicity of the substrates evaluated from relative elution volume in reversed-phase HPLC. The correlation suggests that the hydrophobicity of the C-terminal amino acid is a major factor in governing the stability of the enzyme–substrate complex. The difference in the slope of the linear-regression lines seems to reflect the degree of relative hydrophobicity of the binding pockets in carboxypeptidase-Y and carboxypeptidase-A.