Enzymatic Susceptibility of Comparable N-acylated

The soluble L peptidases of tissue homogenates comprise a number of systems (1, 2), one of which, renal acylase I, has been studied to a considerable extent in this Laboratory (3-6).’ Renal acylase I is essentially an intracellular carboxypeptidase, for it reqdires the presence of a free cr-carboxyl group in the susceptible substrate (5). Apart from this, its specificity requirements are broader than those of the classic pancreatic carboxypeptidase, for, unlike the latter enzyme, (a) it acts equally well upon cyclohexyland phenyl-subst.ituted derivatives, and in general is more effective toward acylated aliphatic amino acids than toward aromatic-substituted amino acids (3); (b) it acts upon N-acylamino acids with a free a-amino group on the acyl radical (4) ; and (c) at an appreciable rate upon certain acylated n-amino acids (3, 6).2 Its action on N-acylated dehydroamino acids has not yet been reported. Pancreatic carboxypeptidase has been reported to be ineffective toward this class of compounds (8). The present study is therefore concerned with the susceptibility of comparable N-acylated L-, D-, and dehydroamino acids toward acylase I and toward homogenates of hog kidney and liver under identical experimental conditions.