Metabolism of glycine by rumen microorganisms.

Rumen microorganisms rapidly metabolized glycine at rates varying from 0.014 to 0.241 mumole of glycine per ml per min. The main metabolic products were carbon dioxide, acetic acid, and ammonia; little glycine was incorporated into bacterial protein. Use of carboxyl or methylene-labeled glycine showed that the carbon dioxide came mainly from the carboxyl of glycine, whereas both carbons of acetic acid were derived partly from the methylene carbon of glycine and partly from carbon dioxide. The ratio of carbon-14 to nitrogen-15 in glycine isolated from the protein of rumen bacteria incubated in the presence of N(15)- and C(14)-labeled glycine indicated that most of the extracellular glycine incorporated into protein was incorporated without intervening deamination.