Protease-Catalyzed Synthesis of Oligo-l-Glutamic Acid from l-Glutamic Acid Diethyl Ester

Abstract

A synthesis of l-glutamic acid oligopeptide from l-glutamic acid-α,γ-diethyl ester hydrochloride is demonstrated by the use of papain and α-chymotrypsin. An examination of this polymerization reaction by turbidimetry, a micro-biuret assay and gel chromatography showed that effective synthesis was achieved at pH 7 ~ 8.5 in phosphate buffer at 25 ~ 35°C for both enzymes. It was revealed by gel chromatography that a higher molecular peptide fraction was accumulated during the reaction as a precipitate, which was determined to be peptides composed of 5 to 9 glutamic acid residues. When 100 mM of the substrate was incubated with 10 μM of papain, more than an 80% overall reaction yield (42% as a precipitate) was attained after 24 hr of the reaction.