Conditions for lysinoalanine formation during exposure of protein to alkali.

A broad range of conditions was used for lysinoalanine formation in ribonuclease A and lysozyme. High alkali concentrations and high temperatures accelerated the production of lysinoalanine, but only limited amounts of lysinoalanine, less than that corresponding to the lysine and cystine residues in the original protein, were generated in the proteins tested. Neither aggregation nor extensive hydrolysis of protein was observed when the maximum amounts of lysinoalanine were generated. Tryptic hydrolysis of proteins decreased lysinoalanine formation. Addition of derivatives of lysine or cystine to the protein solution prior to alkaline treatment did not increase the amount of lysinoalanine formed. These data support the suggestion of Bohak (Z. Bohak, J. Biol. Chem., 239, 2878_??_2887 (1964)) that lysinoalanine formation is an intramolecular reaction in the protein molecule and that some intrinsic features in the amino acid sequence would facilitate lysinoalanine formation. These suggestions are consistent with the results found for soybean protein and casein.