PHOSPHORYLATION OF SYNTHETIC PEPTIDE ANALOGS OF THE PHOSPHORYLATABLE SITE OF PHOSPHORYLASE-B WITH PHOSPHORYLASE-KINASE

A synthetic octapeptide of the phosphorylatable site of phosphorylase and its analogs were used to determine the specificity of nonactivated phosphorylase kinase. By substitution of each of six amino acid residues (lysine11, glutamine12, isoleucine13, serine14, valine15, and arginine16), it was found that these residues were all important in the enzyme recognition. Valine15 was more important than isoleucine13, when either valine15 or isoleucine13 was substituted by glutamic acid. A peptide containing two isoleucyl residues (surrounding serine14) had a better phosphorylation rate than a peptide containing two valyl residues. A peptide with a threonine residue instead of serine could be phosphorylated but with a low reaction rate. © 1979.