The Reactivity of SH Groups in Proteins

Abstract

The reactivity of SH groups in proteins varies over a wide range. Hellerman et al. (1943) and later Barron (1951) divided the SH groups of proteins into three types: rapidly reacting, sluggishly reacting, and “masked” or “buried.” According to Barron, SH groups of the first type react readily with nitroprusside and with mild oxidizing agents such as ferricyanide, porphyrindin, and o-iodosobenzoate. SH groups of the second type do not give the nitroprusside reaction, and react only with stronger oxidizing agents (e.g., iodine) and with mercaptide-forming reagents (p-mercuribenzoate and organic arsenical compounds). To the third group belong the SH groups that can be detected only after denaturation of the protein, i.e., after destruction of its secondary and tertiary structure.