Acetyl-CoA production and utilization during growth of the facultative methylotroph Pseudomonas AM1 on ethanol, malonate and 3-hydroxybutyrate.
In Pseudomonas AM1, conversion of 3-hydroxybutyrate to acetyl-CoA is mediated by an inducible 3-hydroxybutyrate dehydrogenase, an acetoacetate: succinate coenzyme A transferase (specific for succinyl-CoA) and an inducible beta-ketothiolase. Ethanol is oxidized to acetate by the same enzymes as are involved in methanol oxidation to formate. An inducible acetyl-CoA synthetase has been partially purified and characterized; it is essential for growth only on ethanol, malonate and acetate plus glyoxylate, as shown by the growth characteristics of a mutant (ICT54) lacking this enzyme. Free acetate is not involved in the assimilation of acetyl-CoA, and hydroxypyruvate reductase is not involved in the oxidation of acetyl-CoA to glyoxylate during growth on 3-hydroxybutyrate. A mutant (ICT51), lacking 'malate synthase' activity has been isolated and its characteristics indicate that this activity is normally essential for growth, of Pseudomonas AM1 on ethanol, malonate and 3-hydroxybutyrate, but not for growth on other substrates such as pyruvate, succinate and C1 compounds. The growth properties of a revertant (ICT51R) and of a mutant lacking malyl-CoA lyase (PCT57) indicate that an alternative route must exist for assimilation of compounds metabolized exclusively by way of acetyl-CoA.
D000106:Acetate-CoA Ligase / Q000378:metabolism; D000105:Acetyl Coenzyme A / Q000096:biosynthesis / Q000378:metabolism*; D002474:Cell-Free System; D003065:Coenzyme A / Q000031:analogs & derivatives*; D000431:Ethanol / Q000378:metabolism*; D006885:Hydroxybutyrates / Q000378:metabolism*; D008314:Malonates / Q000378:metabolism*; D009154:Mutation; D007652:Oxo-Acid-Lyases / Q000378:metabolism; D010770:Phosphotransferases / Q000378:metabolism; D011549:Pseudomonas / Q000201:enzymology / Q000378:metabolism*
D006885:Hydroxybutyrates; D008314:Malonates; D000431:Ethanol; D000105:Acetyl Coenzyme A; D010770:Phosphotransferases; D007652:Oxo-Acid-Lyases; D000106:Acetate-CoA Ligase; D003065:Coenzyme A