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ABSTRACT
Phosphorylation of an amino acid residue close to the peptide bond, which is a target of a specific proteolytic enzyme, seems to cause inhibition of such a cleavage. This finding may have a number of important consequences. The effect of phosphorylation of a model peptide on its proteolytic cleavage by trypsin was studied. The velocity of peptide bond cleavage of nonphosphorylated synthetic peptide was compared with cleavage velocity of the same bond of synthetic peptide phosphorylated on serine residue located in closed proximity of the specifically cleaved peptide bond. It was shown that the enzymatic cleavage was inhibited by phosphorylation of mentioned amino acid residue. Reversed-phase high-performance chromatography (RP-HPLC) was used for the fast and reliable analysis of reaction mixtures. Influence of the addition of alkaline phosphatase on proteolytical cleavage of casein was also investigated. RP-HPLC peptide maps of β-casein cleaved by trypsin in the presence and absence of alkaline phosphatase were compared. It was proven that the action of acid phosphatase affects the composition of the resulting proteolytic digest.
ACKNOWLEDGMENT
The support of this research by the Grant Agency of the Czech Republic is gratefully acknowledged, Grant No. 203/98/P201.