Identification and properties of reactive sites in protein capable of binding carbon dioxide in a gas-solid phase system.

Abstract

In order to identify the functional groups which really contribute to the carbon dioxide gas adsorption by proteins, epsilon-amino groups of lysine residues of egg albumin were chemically modified with trinitrobenzene sulfonic acid to various degrees. About 60% of the total amount of carbon dioxide gas absorbed by solid egg albumin diminished by complete modification. The amount of carbon dioxide gas adsorbed by lysozyme, its hydrolyzates and gelatin hydrolyzates depended upon the lysine content, arginine content and average molecular weight. The good correlation was obtained between the amount of carbon dioxide gas absorbed and the total of lysine and arginine content of them. The ability of carbon dioxide gas adsorption by alpha-amino group of amino acids and oligopeptides was found to be developed by the elongation of the peptide chain of glycine and other amino acid, by the removal of alpha-carboxyl group of histidine and tyrosine to corresponding amines and by the esterification of alpha-carboxyl group of leucine with p-nitrophenol. These results clearly indicate that CO2 binding sites in protein in the gas-solid phase system are epsilon-amino, alpha-amino and guanidinium groups.