title: Common enzymes of branched-chain amino acid catabolism in Pseudomonas putida.
abstract: Two types of Pseudomonas putida PpG2 mutants which were unable to degrade branched-chain amino acids were isolated after mutagenesis and selection for ability to grow on succinate, but not valine, as a sole source of carbon. These isolates were characterized by growth on the three branched-chain amino acids (valine, isoleucine, and leucine), on the corresponding branched-chain keto acids (2-ketoisovalerate, 2-keto-3-methylvalerate, and 2-ketoisocaproate), and on other selected intermediates as carbon sources, and by their enzymatic composition. One group of mutants lost 2-ketoisovalerate-inducible branched-chain keto acid dehydrogenase that was active on all three keto acids. There was also a concomitant loss of ability to grow on all three branched-chain amino acids as well as on all three corresponding keto acids, but there was retention of ability to use subsequent intermediates in the catabolism of branched-chain amino acids. Another type of mutant showed a marked reduction in branched-chain amino acid transaminase activity and grew poorly at the expense of all three amino acids, but it utilized subsequent intermediates as carbon sources. Both the transaminase and branched-chain keto acid dehydrogenase mutants retained the ability to degrade camphor. These findings are consistent with the view that branched-chain amino acid transaminase and branched-chain keto acid dehydrogenase are common enzymes in the catabolism of valine, isoleucine, and leucine.
mesh_terms: D000429:Alcohol Oxidoreductases / Q000096:biosynthesis* / Q000378:metabolism; D000476:Alkanesulfonates; D000596:Amino Acids; D002164:Camphor / Q000378:metabolism; D002474:Cell-Free System; D003470:Culture Media; D007532:Isoleucine / Q000378:metabolism*; D007651:Keto Acids / Q000378:metabolism*; D007930:Leucine / Q000378:metabolism*; D009153:Mutagens; D009154:Mutation; D011549:Pseudomonas / Q000201:enzymology* / Q000254:growth & development / Q000378:metabolism; D013237:Stereoisomerism; D013386:Succinates / Q000378:metabolism; D000637:Transaminases / Q000096:biosynthesis* / Q000378:metabolism; D014633:Valine / Q000378:metabolism*
chemical_list: D000476:Alkanesulfonates; D000596:Amino Acids; D003470:Culture Media; D007651:Keto Acids; D009153:Mutagens; D013386:Succinates; D007532:Isoleucine; D002164:Camphor; D000429:Alcohol Oxidoreductases; D000637:Transaminases; D007930:Leucine; D014633:Valine