Analytical Methods for the Detection and Purification of ε-Poly-L-lysine for Studying Biopolymer Synthetases, and Bioelectroanalysis Methods for Its Functional Evaluation

This article describes new analytical methods for studying biopolymer epsilon-poly-L-lysine (epsilon PL). The produced amount of ePL in culture broth can be determined based on the precipitation of polycationic epsilon PL with a colored heteropolymolybdate anion and the color change of the supernatant. The product can be separated and purified by precipitation with the tetraphenylborate anion and reprecipitation in the form of the hydrochloride salt. These methods have been applied advantageously to the screening of epsilon PL-synthetase. Also, pyrophosphate can be determined colorimetrically based on the formation of 18-molybdopyrophosphate species. The pyrophosphate determination has been successfully applied to the assay of adenylation enzyme, which plays important roles in the biosynthetic mechanism. Under certain conditions, epsilon PL associates with a redox enzyme, glucose oxidase. The effect of the adduction on the stability and reaction rate of the enzyme can be evaluated by measuring the bioelectrocatalytic current, which is related to the enzyme activity. Electrochemical studies showed new applications of epsilon PL as an enzyme stabilizer and a reaction enhancer.