although the tripeptides glu-o-phosphoserine-tyr and glu-o-phosphoserine-leu have been identified in embryonic bovine enamel proteins , 1 , 2 the issue of whether both sequences occur in each of the phosphopeptides , or whether certain sequences occur in specific peptides only , has recently been resolved by isolating homogeneous samples of e33 and e44 .
C0031684
phosphopeptides
C0030956
peptides