Digestibility of Acetylated and Succinylated Proteins by Pepsin-Pancreatin and Some Intracellular Peptidases

The molecular sizes of hydrolysates of acetylated and succinylated caseins by pepsin-pancreatin were examined by gel filtration on Sephadex G-15. There were more large peptides (average residual number > 15) in the hydrolysates of the acylated caseins than there were in the hydrolysate of unmodified casein. In these large peptides from the acylated caseins the contents of N^ε-acyl-lysines were high. The digestibility of N^ε-acetyl and N^ε-succinyl lysine bonds in peptides by aminopeptidases (EC 3.4.11.1) and (EC 3.4.11.2)] and watermelon carboxypeptidase model enzyme of cathepsin A (EC 3.4.16.1)] was examined using digest of acylated caseins by pepsin, trypsin and α-chymotrypsin and some synthetic peptides. All peptidases released either N^ε-acetyl or N^ε-succinyl-lysine from peptides.

The hydrolytic processes of acetylated and succinylated proteins before and after intestinal absorption are discussed.