Dehydropeptidase activity in certain animal and plant tissues.

In 1932, Bergmann and Schleich (1) observed that glycerol extracts of swine kidney and pancreas possess the capacity of hydrolyzing glycyldehydrophenylalanine (glycyl-cr-aminophenylacrylic acid) to glycine, ammonia, and phenylpyruvic acid. To the enzyme system responsible, whose distinction from dipeptidase, carboxypeptidase, and aminopeptidase was demonstrated, they gave the designation of dehydropeptidase. This enzyme system was not further investigated until recently, when, by using acetyldehydroalanine, chloroacetyldehydroalanine, and glycyldehydroalanine as substrates, it was noted that (1) glycyldehydroalanine was hydrolyzed with great rapidity in aqueous extracts of all animal and plant tissues studied, yielding products which included equivalent amounts of ammonia and pyruvic acid (2-4) ; (2) acetyldehydroalanine and chloroacetyldehydroalanine were hydrolyzed in extracts only of kidney and liver and of a few plant tissues to yield equivalent amounts of ammonia and pyruvic acid; (3) this distribution in different, tissues capable of splitting glycyldehydroalanine and chloroacetyldehydroalanine suggested the existence of at least two different dehydropeptidases, for one of which, designated dehydropeptidase I, the former substrate was suitable, and for the other, designated dehydropeptidase II, the latter substrate was suitable (2). This distinction has since been established by Shack who separated the two enzymes by fractional alcohol precipitation at low temperature.’ Furthermore, it has been found that the aliphatic dehydropeptides possess a characteristic absorption in the ultraviolet region which disappears as the substrates are hydrolyzed; accordingly, an alternative method to that of the chemical determination of ammonia and pyruvic acid is available for following the course of dehydropeptidase activity in tissue preparations (2-4). Finally, the ready enzymatic degradation of cystine peptides (2) and of di(glycylamino)propionic acid (5, 6) to products which include equivalent amounts of ammonia and pyruvic acid suggests possible physiological precursors of the dehydropeptides. The purpose of the present communication is to supplement these findings (1) by reporting the relative susceptibility of a wide variety of dehydropeptides, some of them new, to enzymatic hydrolysis by a number of animal