Mechanism of inhibition of phosphatase activity by glycine.

Glycine and other a-amino acids in very low concentrations have been shown to increase the apparent activity of several enzymes: urease, the various amylases, pancreatic lipase, tyrosinase, yeast peptidase, and the phosphatases (l-3). Occasional observations in the literature indicate, however, that higher concentrations of a-amino acids exert an inhibiting effect on enzyme action (1,4-7). Thus Kato’s study of the effect of glycine on urease activity contains data showing that glycine inhibits this enzyme at concentrations greater than about 0.04 M (4). Bodansky observed that tissue phosphatase activity was retarded by glycine and other a-amino acids in concentrations greater than about 0.01 to 0.001 M, depending upon the particular a-amino acid employed (1). In view of these instances of enzyme inhibition by a-amino acids, it was considered that the nature of the effect warranted more complete investigation. The present paper is concerned with the mechanism of inhibition of bone and intestinal phosphatase preparations by glycine.