Acetylmethionine as a source of methionine for the rat.

A-Acetyl-L-methionine and N-acetyl-D-methionine were compared with L-methionine and D-methionine as sources of methionine. These derivatives were added to a sulfer amino acid-limited diet containing 10% soybean protein isolate. Weight gains, food intake, and protein efficiency ratios (PER) were determined in growing rats. N-Acetyl-L-methionine, L-methionine, and D-methionine produced an equivalent growth response and increase in PER above that of the basal diet. There was no response to supplementation with N-acetyl-D-methionine. An equivalent maximum growth response of rats fed-L-methionine or N-acetyl-D-methionine. An equivalent maximum growth response of rats fed L-methionine or N-acetyl-L-methionine was obtained when the total dietary sulfur amino acids compromised 0.36-0.41% of the diet. The nutritional similarities of methionine and N-acetyl-L-methionine suggest that the latter may be useful as a supplement to diets containing vegetable proteins that are deficient in sulfur amino acids.