Rich analytic toolbox for the exploration, characterization, screening, and application studies of ω-transaminases

Omega-transaminases (ωTAs) constitute an important class of biocatalysts in the pharmaceutical, agrochemical, and fine chemical industries, because of their generally good performance in the efficient, enantiospecific, and environment-friendly synthesis of chiral amines that possess diverse chemical structures and biological activities. However, their practical applications are often hindered by unfavorable reaction equilibria, product inhibition, limited robustness, and relatively small accommodation for substrates. Many efforts, including the exploration of novel enzymes from various environments and the targeted engineering of identified enzymes, have been made to develop more specific and efficient ωTA catalysts. A simple, rapid, and accurate evaluation of enzyme activity is important. In addition to the classic chromatography-based methods, to date, at least 18 analytic methods, which are based on cell growth or colorimetry/spectrophotometry, pH, fluorescence and conductivity changes, have been developed and applied in both qualitative and quantitative analyses of ωTAs. These methods differ in terms of their principles, accuracy, throughput, simplicity, and cost-effectiveness. Here, we present a detailed examination of the advantages and drawbacks of these methods. Guidance for method selection from the perspective of practical applications is proposed to assist investigators in choosing appropriate methods according to different research purposes and existing conditions.