Studies of the Synthetic Model Enzyme. The Synthesis of Cyclo(His–Glu–Cys-d-Phe–Gly)2 as the Esterase Model

To study the mechanism of enzyme action, cyclo(His–Glu–Cys-d-Phe–Gly)2 was prepared as an esterase model from the corresponding linear decapeptide by the azide methods. The esterase-like activity of this cyclic decapeptide in reaction to p-nitrophenyl acetate was three times greater than that of the linear decapeptide, the curve of the catalytic coefficient versus the different pH is of a bell type, and the optimum pH was recorded at about 7.6. The kinetics of the hydrolysis obeyed Michaelis-Menten’s typical equation.