Fiber-optic in situ analysis of the catalytic kinetics of the alliin/alliinase system

In this work, we studied the catalytic kinetics of the alliin/alliinase system using a fiber-optic in situ monitoring system (fiber-optic drug dissolution test system, FODT) to explore the application of a fiber-optic sensor analysis technique in the process of monitoring catalytic kinetics. According to Lambert–Beerʹs law and with the assistance of the computational relationship of alliin, allicin and pyruvate, we established two mathematical models, including obtaining the absorptivity of each substance in the reaction and looking at the products as a whole. According to the UV spectra of alliin, alliinase, sodium pyruvate, an allicin solution and the analyte corresponding to the allicin peak extracted from an HPLC/PDA chromatogram, an optical probe with a 5-mm gap was chosen for the measurement, and 230 nm was chosen as the detection wavelength during the catalysis reaction. Then, we determined the value of every parameter in the mathematical model at 230 nm and recorded the information into the workstation. A certain concentration of alliinase was well-mixed with a series of alliin solutions in the volume ratio 1:1, and the concentration variation of alliin was monitored in real time. The maximum reaction rates for various concentrations of the substrate were obtained using Origin 7.5 software. To this end, a double-reciprocal plot was used to calculate the parameters of the catalytic kinetics of the alliin/alliinase system, including the Michaelis constant (Km) and the maximum velocity (Vmax), which was compared to HPLC results.