title: Studies on the in vivo utilisation and the in vitro enzymatic reduction of methionine sulphoxide in rats and rat tissues.
abstract: The aim of the present study was to gather information on the utilisation of methionine sulphoxide as a source of methionine in the rat, and to find out where and to what extent reduction of methionine sulphoxide takes place. Carcass analysis of rats fed methionine sulphoxide and cystine as the only sulphur-containing amino acids showed that methionine had been formed. This is taken as evidence for reduction and utilisation of methionine sulphoxide in rats. Enzymatic reduction of methionine sulphoxide in different rat tissues was not detected using various reducing agents and assay conditions. Bacteria were found to reduce methionine sulphoxide, with eventual secretion of methionine into the medium. The reduction was stereospecific as only L-methionine-l-sulphoxide was reduced. Weight gain and content of methionine sulphoxide in blood plasma and intestine were similar in rats fed in the presence or absence of antibiotics, indicating that bacteria in the intestine were not responsible for the utilisation of methionine sulphoxide in the rat.
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001835:Body Weight / Q000187:drug effects; D004044:Dietary Proteins / Q000008:administration & dosage; D007413:Intestinal Mucosa / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008297:Male; D008715:Methionine / Q000031:analogs & derivatives* / Q000097:blood / Q000378:metabolism; D010084:Oxidation-Reduction; D051381:Rats
chemical_list: D000900:Anti-Bacterial Agents; D004044:Dietary Proteins; D008715:Methionine; C013111:methionine sulfoxide