[Effect of non-enzymic glycosylation on reactivity in proteolysis]

The nonenzymic glucation of most proteins occurs only at epsilon-amino groups of lysine residues. Hydrolysis catalyzed by bovine trypsin, porcine trypsin and pineapple bromelian were studied using native and glucated proteins as substrates. Glucosylated ovalbumin, human serum albumin, gamma-globulin and myoglobin show reduced susceptibility to degradation by trypsin as compared to the nonglucated proteins, apparently by direct modification of lysine residues. Trypsin cleaves at substrate arginine and lysine peptides bonds. Bromelian, a less specific enzyme, shows similar hydrolysis rates for native casein, ovalbumin and myoglobin, and identical rates for glucated hemoglobin and myoglobin. Bovine trypsin showed 100% decrease in enzymatic activity with glucated human serum albumin and gamma-globulin and pineapple bromelian with human serum albumin.