Figure 4.

A, reaction of FdsABG with saturated CO₂(aq) and 300 μm NADH in 20 mm Bis-Tris propane (final pH 6.3) performed at 30 °C under anaerobic conditions. The arrow indicates addition of enzyme. B, ion chromatography analysis of the product of the reaction in A as described under “Experimental procedures.” Retention times are indicated with arrows for formate (5.9 min), bicarbonate (7.4 min), and NADH/NAD⁺ (11.2 min). C, ¹³C NMR spectrum for [¹³C]formate generated enzymatically with dissolved [¹³C]bicarbonate at 161.08 ppm. D, ¹³C NMR standard spectrum with 100 mm natural abundance formic acid brought to pH ∼6.3 with sodium bicarbonate. μS, microsiemens.