Enzymatic reduction of protein-bound methionine sulfoxide.

Abstract
An enzyme that catalyzes the reduction of methionine sulfoxide residues in ribosomal protein L12 was partially purified from Esherichia coli extracts. Methionine sulfoxide present in oxidized [Met]enkephalin is also reduced by the purified enzyme. The enzyme is different from a previously reported E. coli enzyme that catalyzes the reduction of methionine sulfoxide to methionine. Extracts of rat tissues, Euglena gracilis, Tetrahymena pyriformis, HeLa [human cervical cancer] cells and spinach also can catalyze the reduction of methionine sulfoxide residues in protein.