Tissue Metabolism of Methionine in Sheep

Abstract

The rate of oxidization of the carboxyl and methyl carbons of (I4C]methionine to CO2 by homogenates of liver, kidney cortex, pancreas, muscle and small intestinal mucosa was studied in two breeds of sheep (Merino and Poll Dorset Horn) at three ages (2 weeks, 3 months, 4 years). Sodium a-keto-,),methiolbutyrate (0·4 mM) stimulated production of CO2 from the carboxyl carbon of methionine, but not from the methyl carbon. Sodium pyruvate did not affect the recovery of CO2 from either carboxyl or methyl of methionine. Sodium formate (15 mM) suppressed the conversion of the methyl carbon of methionine to CO2 by liver and kidney homogenates to 4 and 50%, respectively, of control values, but did not affect the percentage of carboxyl carbon of methionine recovered in CO2 with either tissue. With addition of S-methyl-L-cysteine (40 mM) and 3-methylthiopropionate (10 mM) the percentage of methyl and carboxyl carbons recovered in CO2 was reduced to about 20% of control values in homogenates of both tissues.