title: Identification of metabolic pathways involved in the biosynthesis of flavor compound 3-methylbutanal from leucine catabolism by Carnobacterium maltaromaticum LMA 28.
abstract: Carnobacterium maltaromaticum strains are widely found in food including fish, meat and some dairy products. Producing a malty/chocolate like aroma due to 3-methylbutanal from the catabolism of leucine is a general characteristic of this species. In this study, we investigated metabolic routes responsible for the biosynthesis of this flavor compound from the catabolism of leucine in C. maltaromaticum LMA 28, a strain isolated from mold ripened soft cheese. Depending on the lactic acid bacterium, leucine can be converted into 3-methylbutanal following two possible metabolic pathways: either directly by α-ketoacid decarboxylase (KADC) pathway or indirectly by α-ketoacid dehydrogenase (KADH) pathway. Both KADC (41.0±3.0 nmol/mg protein/min) and KADH (1.43±0.62 nmol/mg protein/min) activities were detected and determined in vitro in C. maltaromaticum LMA 28. C. maltaromaticum LMA 28 slightly reduced the production of 3-methylbutanal from leucine in the presence of a specific inhibitor of KADH enzyme complex, i.e. sodium meta-arsenite, suggesting that both pathways were involved in vivo in leucine catabolism. Moreover the presence of genes encoding aminotransferase, glutamate dehydrogenase, α-ketoacid decarboxylase, α-ketoacid dehydrogenase and aldehyde dehydrogenase was confirmed. C. maltaromaticum is then the first lactic acid bacterium in which presence of both metabolic routes responsible for the biosynthesis of 3-methylbutanal from leucine catabolism was confirmed in vitro and in vivo as well.
authors: Laboratoire d'ingénierie des biomolécules, Université de Lorraine, 2 Avenue de la Forêt de Haye B.P. 172, 54505 Vandoeuvre-lès-Nancy, France.
authors: Muhammad Inam
authors: MI
authors: Afzal
authors: Stéphane
authors: S
authors: Delaunay
authors: Cédric
authors: C
authors: Paris
authors: Frédéric
authors: F
authors: Borges
authors: Anne-Marie
authors: AM
authors: Revol-Junelles
authors: Catherine
authors: C
authors: Cailliez-Grimal
mesh_terms: D000447:Aldehydes / Q000378:metabolism*; D056573:Carnobacterium / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D002611:Cheese / Q000382:microbiology; D004798:Enzymes / Q000378:metabolism; D005421:Flavoring Agents / Q000378:metabolism*; D007777:Lactobacillaceae / Q000378:metabolism; D007930:Leucine / Q000378:metabolism
chemical_list: D000447:Aldehydes; D004798:Enzymes; D005421:Flavoring Agents; C032251:isovalerylaldehyde; D007930:Leucine