15] Deblocking in peptide synthesis with immobilized carboxypeptidase Y

Abstract

This chapter describes carboxypeptidase Y (CPY) that involves the concept of a method for the synthesis of peptides in aqueous systems using very mild conditions for deblocking. Small protected peptides can be deblocked in alcohol/water mixtures. However, as the size of the peptide increases, the solubility decreases. To use the immobilized CPY in the presence of high levels of organic solvent is not possible. CPY is an exopeptidase found in yeast. The enzyme is unusual, because it has a broad specificity. It catalyzes the release of L-amino acids, including proline, from the C terminus of a polypeptide chain. Rates of amino acid release vary but not to the extent exhibited by other exopeptidases such as pancreatic enzymes. CPY also acts as an esterase. It rapidly cleaves the C-terminal alkyl ester group of large and small peptides. In conclusion, immobilized CPY is a versatile tool for the protein chemistry lab. It can be used for deblocking in peptide synthesis, the resolution of racemic mixtures of blocked amino acid esters or peptides, the sequencing of peptides, the total hydrolysis of peptides for analysis, and condensation reactions in peptide synthesis. The attachment of C-terminal amino acid amides may be accomplished using CPY to catalyze the peptide bond formation starting with the peptide ester and the amide. Also, the enzyme should be of interest in peptide modification and fragment condensation of peptides.