Partial purification and characterization of a formylmethionine deformylase from rat small intestine

A formylmethionine deformylase from rat small-intestinal mucosa has been isolated, characterized and partially purified. The enzyme catalyses the release of equimolar amounts of formate and the free amino acid. The deformylase was active against formylmethionine (Km 7.1 mM) and formylnorleucine, but showed reduced activity against formyl-leucine. It was inactive against a range of other polar and nonpolar formyl-amino acids and against formyl di- and tri-peptides. The Mr of the native enzyme was between 45,000 and 66,000, as determined by h.p.l.c. gel permeation. Further purification of the enzyme either by h.p.l.c. ion-exchange chromatography and concanavalin A-Sepharose or by isoelectric focusing yielded a preparation with one predominant band of Mr 50,000 on SDS/polyacrylamide-gel electrophoresis. Bacteria in the intestine present the host with substantial amounts of formylmethionine (fMet) from proteinase and carboxypeptidase digestion of bacterial formyl-peptides in the intestinal lumen. fMet (0.01-1.0 mM) inhibited translation of a test RNA from brome mosaic virus in vitro, indicating that it could have adverse effects on cellular metabolism. Gut epithelial fMet deformylase may be required for deformylation of this exogenous (bacterial) and also endogenous (mitochondrial) fMet.