Blockage of Protein Enzymatic Digestion (Carboxypeptidase‐b) by Heat‐induced Sugar‐lysine Reactions

TO investigate heat‐induced sugar‐lysine reactions in proteins (Mail‐lard browning) solutions of glucose and poly‐L‐lysine (lysine glucose ratio 1:l) were heated at selected temperatures (101—170° C) as a function of time. Spectra of such solutions exhibit absorbance maxima at 287 nm and 330 nm. Heated‐solutions were incubated with carboxypeptidase‐B at 37°C‐24 hr. Lysine released by this digestive enzyme was almost completely stopped after only 12% of the poly‐L‐lysine‐glucose reaction had taken place. Rate constants and activation energies for the poly‐L‐lysine‐glucose reaction and decrease in peptide bond cleavage were calculated. The application of our basic data to in vivo protein digestion is discussed in terms of nutrition and allergic diseases, such as celiac disease.