Succinylation of pepsinogen.

Abstract Succinic anhydride reacts with pepsinogen to form succinylpepsinogen in which the 10 e-amino groups of the lysine residues are succinylated. In addition reaction occurs with 16 tyrosine residues and 10 to 13 hydroxyamino acid residues of the protein. In contrast to the O-succinyltyrosines of succinylpepsinogen which are spontaneously decomposed in 3 to 4 hours, the succinylhydroxyamino acid residues are stable but can be deacylated with hydroxylamine. Succinylation of pepsinogen is accompanied by a decreased susceptibility to activation at pH 2.0. An enzymically active product can be obtained on exposure of succinylpepsinogen to pH 5.0 followed by assay for proteolysis of hemoglobin at pH 2.0. Succinylation results in a change of the macromolecular conformation of the protein as reflected by a decrease of λc from 236 to 222 mµ and a decrease in [α]366 from -222 to -320 and of [R']227 from -3978 to -5200.