Search for regular polypeptides possessing esterase properties. I. Polypeptides containing tyrosine and glutamic acid residues

Abstract

An investigation has been made of the catalytic properties in relation to the hydrolysis of p-NPA of six polypeptides of regular structure: H-[Glu-Tyr]n-OH (1), H-[Glu2-Tyr]n-OH (2), H-[Glu-Tyr3]n-OH (3), H-[Glu3-Tyr]n-OH (4), H-[Glu3-Tyr]n-OH (5), and H-[Glu-Tyr2]n]-OH (6). It has been shown that polypeptides (I), (III), and (IV) catalyze the hydrolysis of p-NPA (p-nitrophenyl acetate). An enzyme-like type of catalysis has been found. Some catalytic characteristics have been calculated and the dependence of the rate of hydrolysis on the pH of the medium, the temperature, and the concentration of p-NPA have been discussed. The structures of the catalytically active and catalytically inactive polypeptides have been studied by the circular dichroism method. It has been shown that under conditions in which the catalytic properties of polypeptides are shown to the maximum degree there is a structure of the random coil type. The catalytic activity falls or disappears completely when ordered fragments of the α-helix and β-structure types appear in the structure. It has been found that polypeptide (I) possesses the maximum catalytic activity. It exceeds the activity of a copolymer of the same amino acids by an order of magnitude.