The biosynthesis of protein. 1. The uptake of glycine, serine, valine and lysine by the mammary gland of the rabbit

Abstract

C14 labelled valine, lysine, serine and glycine were used in tests establishing activity/time curves for the milk and plasma proteins. Blood amino acids were shown to contribute most of the N for the synthesis of the milk proteins. Comparison of the specific activities of the labelled amino acids isolated from the radioactive milk proteins indicated the existence of at least 2 forms of precursors contributing amino acid residues for the formation of milk protein. Injn. of plasma protein labelled with C14 glycine and C14 serine resulted in only a very slight activity in the milk proteins. A method for the quantitative estimation of glycine in protein by means of its dinitrophenyl derivative is appended.