title: Branched-chain 2-keto acid decarboxylases derived from Psychrobacter.
abstract: The conversion of branched-chain amino acids to branched-chain acids or alcohols is an important aspect of flavor in the food industry and is dependent on the Ehrlich pathway found in certain lactic acid bacteria. A key enzyme in the pathway, the 2-keto acid decarboxylase (KDC), is also of interest in biotechnology applications to produce small branched-chain alcohols that might serve as improved biofuels or other commodity feedstocks. This enzyme has been extensively studied in the model bacterium Lactococcus lactis, but is also found in other bacteria and higher organisms. In this report, distinct homologs of the L. lactis KDC originally annotated as pyruvate decarboxylases from Psychrobacter cryohalolentis K5 and P. arcticus 273-4 were cloned and characterized, confirming a related activity toward specific branched-chain 2-keto acids derived from branched-chain amino acids. Further, KDC activity was confirmed in intact cells and cell-free extracts of P. cryohalolentis K5 grown on both rich and defined media, indicating that the Ehrlich pathway may also be utilized in some psychrotrophs and psychrophiles. A comparison of the similarities and differences in the P. cryohalolentis K5 and P. arcticus 273-4 KDC activities to other bacterial KDCs is presented.
authors.affiliation: Department of Bioproducts and Biosystems Engineering, University of Minnesota, St. Paul, MN, USA; Biotechnology Institute, University of Minnesota, St. Paul, MN, USA.
authors.forename: Jiashi
authors.initials: J
authors.lastname: Wei
authors.forename: Jacobe G
authors.initials: JG
authors.lastname: Timler
authors.forename: Carolann M
authors.initials: CM
authors.lastname: Knutson
authors.forename: Brett M
authors.initials: BM
authors.lastname: Barney
mesh_terms: D000426:Alcohol Dehydrogenase; D000597:Amino Acids, Branched-Chain / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002262:Carboxy-Lyases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D044096:Psychrobacter / Q000201:enzymology* / Q000235:genetics; D013696:Temperature
chemical_list: D000597:Amino Acids, Branched-Chain; D001426:Bacterial Proteins; D000426:Alcohol Dehydrogenase; D002262:Carboxy-Lyases
keywords: KdcA; Psychrobacter arcticus; Psychrobacter cryohalolentis; isoamyl alcohol; keto acid decarboxylase