title: Glutamate dehydrogenase activity can be transmitted naturally to Lactococcus lactis strains to stimulate amino acid conversion to aroma compounds.
abstract: Amino acid conversion to aroma compounds by Lactococcus lactis is limited by the low production of alpha-ketoglutarate that is necessary for the first step of conversion. Recently, glutamate dehydrogenase (GDH) activity that catalyzes the reversible glutamate deamination to alpha-ketoglutarate was detected in L. lactis strains isolated from a vegetal source, and the gene responsible for the activity in L. lactis NCDO1867 was identified and characterized. The gene is located on a 70-kb plasmid also encoding cadmium resistance. In this study, gdh gene inactivation and overexpression confirmed the direct impact of GDH activity of L. lactis on amino acid catabolism in a reaction medium at pH 5.5, the pH of cheese. By using cadmium resistance as a selectable marker, the plasmid carrying gdh was naturally transmitted to another L. lactis strain by a mating procedure. The transfer conferred to the host strain GDH activity and the ability to catabolize amino acids in the presence of glutamate in the reaction medium. However, the plasmid appeared unstable in a strain also containing the protease lactose plasmid pLP712, indicating an incompatibility between these two plasmids.
authors.affiliation: Institut National de la Recherche Agronomique, Unité de Biochimie et Structure des Protéines, 78352 Jouy en Josas, France.
authors.forename: Catherine
authors.initials: C
authors.lastname: Tanous
authors.forename: Emilie
authors.initials: E
authors.lastname: Chambellon
authors.forename: Dominique
authors.initials: D
authors.lastname: Le Bars
authors.forename: Gilbert
authors.initials: G
authors.lastname: Delespaul
authors.forename: Mireille
authors.initials: M
authors.lastname: Yvon
mesh_terms: D000596:Amino Acids / Q000378:metabolism*; D001483:Base Sequence; D002104:Cadmium / Q000494:pharmacology; D002611:Cheese / Q000382:microbiology; D004269:DNA, Bacterial / Q000235:genetics; D024881:Drug Resistance, Bacterial / Q000235:genetics; D015870:Gene Expression; D022761:Gene Transfer, Horizontal; D005798:Genes, Bacterial; D005968:Glutamate Decarboxylase / Q000235:genetics* / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D013294:Lactococcus lactis / Q000187:drug effects / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism*; D009812:Odorants; D010649:Phenylalanine / Q000378:metabolism; D010957:Plasmids / Q000235:genetics; D015032:Zinc / Q000494:pharmacology
chemical_list: D000596:Amino Acids; D004269:DNA, Bacterial; D002104:Cadmium; D010649:Phenylalanine; D005968:Glutamate Decarboxylase; D015032:Zinc