Excess of threonine compared with serine promotes threonine aldolase activity in Lactococcus lactis IL1403.
Lactococcus lactis is an important lactic acid starter for food production as well as a cell factory for production of food grade additives, among which natural flavour production is one of the main interests of food producers. Flavour production is associated with the degradation of amino acids and comprehensive studies are required to elucidate mechanisms behind these pathways. In this study using chemically defined medium, labelled substrate and steady-state cultivation, new data for the catabolism of threonine in Lc. lactis have been obtained. The biosynthesis of glycine in this organism is associated with the catabolic pathways of glucose and serine. Nevertheless, if threonine concentration in the growth environment exceeds that of serine, threonine becomes the main source for glycine biosynthesis and the utilization of serine decreases. Also, the conversion of threonine to glycine was initiated by a threonine aldolase and this was the principal pathway used for threonine degradation. As in Streptococcus thermophilus, serine hydroxymethyltransferase in Lc. lactis may possess a secondary activity as threonine aldolase. Other catabolic pathways of threonine (e.g. threonine dehydrogenase and threonine dehydratase) were not detected.
Tallinn University of Technology, Department of Chemistry, Akadeemia tee 15, Tallinn 12618, Estonia.|Competence Center of Food and Fermentation Technologies, Akadeemia tee 15A, Tallinn 12618, Estonia.
Kadri
K
Aller
Tallinn University of Technology, Department of Food Processing, Ehitajate tee 5, Tallinn 19086, Estonia.|Tallinn University of Technology, Department of Chemistry, Akadeemia tee 15, Tallinn 12618, Estonia.|Competence Center of Food and Fermentation Technologies, Akadeemia tee 15A, Tallinn 12618, Estonia.
Kaarel
K
Adamberg
National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, 12618 Tallinn, Estonia.
Indrek
I
Reile
Tallinn University of Technology, Department of Chemistry, Akadeemia tee 15, Tallinn 12618, Estonia.|Competence Center of Food and Fermentation Technologies, Akadeemia tee 15A, Tallinn 12618, Estonia.
Veronica
V
Timarova
Tallinn University of Technology, Department of Chemistry, Akadeemia tee 15, Tallinn 12618, Estonia.|Competence Center of Food and Fermentation Technologies, Akadeemia tee 15A, Tallinn 12618, Estonia.
Karl
K
Peebo
Tallinn University of Technology, Department of Chemistry, Akadeemia tee 15, Tallinn 12618, Estonia.|Competence Center of Food and Fermentation Technologies, Akadeemia tee 15A, Tallinn 12618, Estonia.
Raivo
R
Vilu
D000596:Amino Acids / Q000378:metabolism; D018533:Biomass; D012696:Glycine Hydroxymethyltransferase / Q000378:metabolism*; D013294:Lactococcus lactis / Q000378:metabolism*; D053858:Metabolic Networks and Pathways; D040901:Proteomics; D012694:Serine / Q000378:metabolism*; D013912:Threonine / Q000378:metabolism*
D000596:Amino Acids; D013912:Threonine; D012694:Serine; D012696:Glycine Hydroxymethyltransferase