Chemical Derivatives of Chymotrypsinogen

The preparation of chemical derivatives of a protein may aid greatly in the elucidation of structure and biological activity.Several excellent reviews on chemical reagents for proteins may be found in the literature (l-3).One desirable characteristic of a substitution reaction is reversibility.This first paper of the series deals with the reaction of a reversible reagent, carbon disulfide, with chymotrypsinogen.This protein is available in high purity and attracts considerable current interest.The following paper deals with the reaction between 0-methylisourea and chymotrypsinogen.Carbon disulfide was suggested for the preparation of protein derivatives by the work of Leonis and Levy (4) on the determination of N-terminal residues of peptides.The free a-amino group was reacted with carbon disulfide at pH 7.5 to form a dithiocarbamate derivative.Acidification led to the separation of the terminal amino acid as the 2-thio-5-thiazolidone.However, with the few proteins which were examined, acidification appeared to reverse the synthetic reaction almost quantitatively.