title: Enzymology of butyrate formation by Butyrivibrio fibrisolvens.
abstract: Butyrivibrio fibrisolvens is a major butyrate-forming species in the bovine and ovine rumen. The enzymology of butyrate formation from pyruvate was investigated in cell-free extracts of B. fibrisolvens D1. Pyruvate owas oxidized to acetylcoenzyme A (CoA) in the presence of CoA.SH and benzyl viologen or flavin nucleotides. The bacterium uses thiolase, beta-hydroxybutyryl-CoA dehydrogenase, crotonase, and crotonyl-CoA reductase to form butyryl-CoA from acetyl-CoA. Reduction of acetoacetyl-CoA to beta-hydroxybutyryl-CoA was faster with NADH than with NADPH. Crotonyl-CoA was reduced to butyryl-CoA by NADH, but not by NADPH, only in the presence of flavin nucleotides. Reduction of flavin nucleotides by NADH was much slower than the flavin-dependent reduction of crotonyl-CoA. This indicates that flavoproteins rather than free flavin participated in the reduction of crotonyl-CoA. Butyryl-CoA was converted to butyrate by phosphate butyryl transferase and butyrate kinase.
mesh_terms: D015094:3-Hydroxyacyl CoA Dehydrogenases / Q000378:metabolism; D000101:Acetyl-CoA C-Acetyltransferase / Q000378:metabolism; D002087:Butyrates / Q000378:metabolism*; D003065:Coenzyme A; D003437:Crotonates; D004746:Enoyl-CoA Hydratase / Q000378:metabolism; D005420:Flavoproteins / Q000378:metabolism; D006089:Gram-Negative Anaerobic Bacteria / Q000201:enzymology*; D007700:Kinetics; D009243:NAD / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D010088:Oxidoreductases / Q000378:metabolism*; D010770:Phosphotransferases / Q000378:metabolism; D011773:Pyruvates / Q000378:metabolism; D014166:Transferases / Q000378:metabolism
chemical_list: D002087:Butyrates; D003437:Crotonates; D005420:Flavoproteins; D011773:Pyruvates; D009243:NAD; D009249:NADP; D010088:Oxidoreductases; D015094:3-Hydroxyacyl CoA Dehydrogenases; C021388:3-hydroxybutyryl-CoA dehydrogenase; D014166:Transferases; D000101:Acetyl-CoA C-Acetyltransferase; D010770:Phosphotransferases; D004746:Enoyl-CoA Hydratase; D003065:Coenzyme A