Synthesis of proline and hydroxyproline peptides; their cleavage by prolinase.

Two types of peptidases are known to hydrolyze peptides containing proline and hydroxyproline. The first of these, prolidase (l-3), attacks peptide bonds involving t,he nitrogen of the imino acids in the typical substrates, glycyl-L-proline and glycylhydroxy+proline. The individuality of this enzyme has already been demonstrated by purification and by specificity studies. The second enzyme, named prolinase (4, 5), has been stated to be specific for proline peptides such as prolylglycine and has been observed in yeast (4), in glycerol extracts of several animal tissues (5), and in aqueous extracts of muscle tissue (6). However, little is known of the properties and specificity of this enzyme. In this communication, further evidence will be presented which indicates t’hat prolinase is distinct from other well characterized peptidases of animal tissues. It had previously been found that the hydrolysis of prolylglycine is activated by Mn++ (6-8). We have now observed t,hat the splitting of related dipeptides containing either L-proline or hydroxy+proline is activated not only by Mn++, but also by Cd++. Since cadmium ion is a potent inhibitor of other peptidases, this finding provides a useful aid in the characterization of prolinase. The synthesis by the carbobenzoxy method of a number of new peptides and derivatives which contain r,-proline and hydroxy+proline is also described.