The determination of amino nitrogen as a measure of the rate and extent of proteolysis

Amino acids in proteins, as shown by Emil Fischer's work, are undoubtedly bound together by peptid (-CO-NH-) linkings, the nitrogen in these linkings being in the imino form. When hydrolysis occurs, the peptid linkings are split, yielding -COOH and -NH₂ derivations. The hydrolysis of each peptid linking, therefore, frees an amino group. Consequently, determination of the amino nitrogen should afford direct chemical measure of the rate and extent to which a protein is hydrolyzed, whether by action of acids, alkalies or enzymes. It should also indicate the relative molecular size of isolated intermediate products, such as albumoses, peptones and peptids, as the larger molecules have relatively more nitrogen in the peptide linkings, and less amino nitrogen. Results have been obtained which indicate that the amino determination fulfills the above requirements of the theory of protein structure, and that it will be of practical value in the study of enzyme action and of the products of partial hydrolysis.