Fig 7. SMC biosynthesis by T. vaginalis CS.

Production of SMC from OPS and CH₃S.Na by recombinant T. vaginalis CS was determined at 37°C. (A) A coupled assay for SMC synthase. The assay couples SMC production by CS to NADH oxidation using MGL and LDH. The rate of NADH oxidation and hence the rate of SMC production can be quantified by measuring the absorbance at 340 nm. (B) The effect of increasing amounts of CS in a coupled assay for SMC biosynthesis. The reaction contained 10 mM OPS, 3 mM CH₃SNa and 0, 1 and 5 μg/ml CS. The graph shows the rate of NADH oxidation which is equivalent to the rate of SMC biosynthesis in the coupled assay. (C) Substrate saturation curve for CH₃SNa. Reactions contained 10 mM OPS, 85 nM CS and 0.25–12 mM sodium CH₃SNa. A plot of enzyme activity against CH₃SNa concentration shows Michaelis-Menten kinetics.