Isolation of phosphorylserine from the plasma phosphoproteins of the laying hen

Abstract

Phosphoryl-serine has been isolated and identified as the sole phosphorylated amino acid present in acid hydrolysates of the plasma phosphoproteins of the laying hen. No phosphorylserine was detected in hydrolysates of plasma from non-laying hens or from cockerels. After the injection of radioactive phosphate the specific radioactivity of phosphorylserine, isolated after different times from two plasma-phospho-protein fractions, was the same in both fractions and similar to that of inorganic phosphate released on incubating the phosphoproteins with dilute alkali.