AMINO ACID SEQUENCE OF 2 O-PHOSPHOSERINE CONTAINING TRIPEPTIDES ISOLATED FROM ORGANIC MATRIX OF EMBRYONIC BOVINE ENAMEL

1. 1.|Two tripeptides containing O-phosphoserine were isolated from an acid hydrolyzate of embryonic, bovine enamel proteins soluble at neutral pH. The tripeptides were purified by ion-exchange chromatography. 2. 2.|One of the tripeptides (Peptide I) contained equimolar amounts of glutamic acid, serine, leucine and phosphorus; the other tripeptide (Peptide II) contained glutamic acid, serine, tyrosine and phosphorus in equimolar amounts. 3. 3.|Sequential analysis by phenylisothiocyanate degradation and dansylation as well as by enzymatic hydrolysis with leucine aminopeptidase and carboxypeptidase A revealed that Peptide I had the sequence of glutamic acid-O-phosphoserine-leucine, while the amino acid sequence of Peptide II was glutamic acid-O-phosphoserine-tyrosine. Enzymatic hydrolysis of both tripeptides with a phosphomonoesterase indicated that phosphorus was covalently bound to the hydroxyl group of serine as a monoester. © 1969.