, 2009). Phosphoribulokinase, Rubisco, acetyl-CoA and propionyl-CoA carboxylase were measured under anoxic conditions radiochemically, as described in Berg

et al. (2010b). Pyruvate carboxylase was measured radiochemically by determining pyruvate-dependent fixation of 14CO2 using a modified method of Mukhopadhyay et al. (2001). The reaction mixture (0.35 mL) contained 100 mM Tris/HCl (pH 7.8), 5 mM dithiothreitol, 200 mM KCl, 1 mM MgCl2, 1 mM ATP, 15 mM NaH14CO3 (3.3 kBq μmol−1), 1 mM NADH SP600125 and cell extract. The reaction was started by the addition of pyruvate (20 mM). Acid-stable 14C was determined as described previously (Hügler et al., 2003). Succinyl-CoA reductase was measured as succinyl-CoA-dependent oxidation of NAD(P)H (Kockelkorn & Fuchs, 2009) and of reduced methyl viologen, respectively (Huber et al., 2008). Succinic semialdehyde reductase was measured as succinic semialdehyde-dependent oxidation Seliciclib chemical structure of NAD(P)H (Kockelkorn & Fuchs, 2009) or of reduced methyl viologen, similar to methyl viologen-dependent succinyl-CoA reductase (Huber et al., 2008), in an assay mixture containing 100 mM MOPS/KOH (pH 7.2), 5 mM MgCl2, 5 mM methyl viologen, 5 mM dithiothreitol and cell extract. The reaction was started by the addition of succinic semialdehyde (2 mM). 4-Hydroxybutyryl-CoA dehydratase activity was measured anoxically using a spectrophotometric

assay with 4-hydroxybutyryl-CoA synthetase from Thermoproteus neutrophilus (Tneu_0420, Ramos-Vera et al., 2011) and crotonyl-CoA hydratase/3-hydroxybutyryl-CoA RVX-208 dehydrogenase from M. sedula (Msed_0399, Ramos-Vera et al., 2011) as coupling enzymes. The assay mixture contained 100 mM Tris/HCl (pH 9.0), 5 mM NAD+, 2.5 mM

ATP, 1 mM CoA, 1 mM MgCl2, 5 mM dithiothreitol, 2 mM 4-hydroxybutyrate, 0.5 U mL−1 4-hydroxybutyryl-CoA synthetase, 0.5 U mL−1 crotonyl-CoA hydratase/3-hydroxybutyryl-CoA dehydrogenase and cell extract. 3-Hydroxybutyryl-CoA dehydrogenase was measured spectrophotometrically as (S)- or (R)-3-hydroxybutyryl-CoA-dependent reduction of NAD+ (Ramos-Vera et al., 2009) or as acetoacetyl-CoA-dependent oxidation of NADH in the following reaction mixture: 100 mM MOPS/KOH (pH 7.8), 5 mM dithiothreitol, 10 mM MgCl2, 0.5 mM NADH, 0.2 mM acetoacetyl-CoA and cell extract. 5-phospho-d-ribose 1-pyrophosphate (PRPP) conversion to ribulose 1,5-bisphosphate was determined as PRPP-dependent fixation of NaH14CO3 into acid-stable products under anoxic conditions. The reaction mixture (0.35 mL) contained 100 mM Tris/HCl (pH 7.8), 5 mM dithiothreitol, 5 mM MgCl2, 15 mM NaH14CO3 (18 kBq μmol−1) and cell extract. After preincubation for 5 min, the reaction was started by the addition of PRPP (1 mM) and the acid-stable 14C was determined after appropriate time intervals (Hügler et al., 2003).