One of our long term interests has been the development of biocatalytic methods for organic synthetic applications. More recently, we have been interested in the utilization of enzymes to catalyze the modification of complex molecules such as proteins and peptides (posttranslational modification) by taking advantage of their chemoselective properties. Consistent with this objective, we intend to focus our attention on three specific projects: [1] To develop rapid sensitive methods for the isolation and identification of the C-terminal fragment of proteins. The first approach entails the enzymatic attachment of a fluorescent amino acid derivative onto the C-terminus of a protein without side reactions; the second method involves the selective epimerization of the C-terminal amino acid. The protein is cleaved into peptide fragments and the non C-terminal peptides are hydrolyzed with carboxypeptidases Y and B. The C-terminal peptide is then isolated and sequenced by Edman chemistry or by FAB mass spectrometry; the third approach takes advantage of the kinetics of chymotryptic cleavage; the first non-ultraviolet light absorbing peptide formed is the C-terminal fragment. [2] To purify and characterize the enzymes present in bacteria that could selectively deacylate N-terminal acetylated proteins and peptide hormones; the unblocked proteins could then be sequenced by Edman chemistry. [3] To develop a general chemoenzymatic asymmetric synthesis of amino acids. This approach involves the lipase-catalyzed enantioselective hydrolysis of 4-substituted-2-phenyl-oxazolin-5-ones to yield optically-active N- benzoyl amino acids of either configuration.
