Biochemical characterization of recombinant 20β-HSDH from B. desmolans ATCC 43058. A: Effect of pH on reductive activity of 20β-HSDH. The 20β-HSDH (0.05 μM) was incubated with cortisol (50 μM) and NADH (150 μM) in sodium citrate buffer (pH 4–6), sodium phosphate buffer (pH 6.5–7.5), Tris-Cl buffer (pH 8–9), and glycine-NaOH buffer (pH 10) for 5 min. B: Effect of pH on oxidative activity of 20β-HSDH. The 20β-HSDH (0.05 μM) was incubated with cortisol (50 μM) and NAD+ (150 μM) in sodium citrate buffer (pH 5–6), sodium phosphate buffer (pH 6.5–7.5), Tris-Cl buffer (pH 8–9), and glycine-NaOH buffer (pH 10–11) for 5 min. One-way ANOVA followed by Tukey’s multiple comparison tests between the pH values using GraphPad Prism 5.04 (GraphPad Software Inc.). C: Cofactor requirement of 20β-HSDH activity from B. desmolans: 20β-HSDH (0.05 μM) was incubated with cortisol (50 μM) and respective pyridine nucleotides (150 μM) in sodium phosphate buffer (pH 7) overnight. D: Michaelis-Menten and Lineweaver-Burk plot of purified 20β-HSDH using cortisol as substrate.