0000000000923291
AUTHOR
C. Labarre
Using specific polyclonal antibodies to study the malolactic enzyme from Leuconostoc oenos and other lactic acid bacteria.
Specific polyclonal antibodies directed against the malolactic enzyme of Leuconostoc oenos were obtained. Despite the homologies between the malolactic enzymes from Leuc. oenos and Lactococcus lactis, no immunological relationship was detected with the L. lactis malolactic enzyme, suggesting differences in their structural organization. The use of the antiserum also demonstrated that the problem of heterologous expression occurring in the recombinant Escherichia coli strain (Labarre et al. 1996a) resulted in a low synthesis of the malolactic enzyme from Leuc. oenos. Moreover, a small amount of the protein was found to be peripherally associated to the membrane of Leuc. oenos.
Cloning of branched chain amino acid biosynthesis genes and assays of alpha-acetolactate synthase activities in Leuconostoc mesenteroides subsp. cremoris.
A genomic library from Leuconostoc mesenteroides subsp. cremoris (Lmc) in Escherichia coli was screened for alpha-acetolactate synthase (ALS) activity using a phenotypic test detecting the production of acetolactate or related C4 derivatives (diacetyl, acetoin or 2,3-butanediol) in the culture. Four recombinant E. coli clones, with plasmids containing overlapping DNA fragments and displaying anabolic ALS activity, were selected. This activity is encoded by an ilvB gene belonging to a putative operon which contains genes highly similar to the genes of the branched chain amino acid (BCAA) operon of Lactococcus lactis subsp. lactis. This putative BCAA operon is not functional as the ilvA gene …