TAILIEUCHUNG - Báo cáo khoa học: Natural-abundance isotope ratio mass spectrometry as a means of evaluating carbon redistribution during glucose–citrate cofermentation by Lactococcus lactis

The cometabolism of citrate and glucose by growing Lactococcus lactisssp. lactis bv. diacetylactis was studied using a natural-abundance stable isotope technique. By a judicious choice of substrates differing slightly in their 13 C/ 12 C ratios, the simultaneous metabolism of citrate and glucose to a range of compounds was analysed. These end-products include lactate, acetate, formate, diacetyl and acetoin. All these products have pyruvate as a common intermediate. | Eur. J. Biochem. 271 4392-4400 2004 FEBS 2004 doi Natural-abundance isotope ratio mass spectrometry as a means of evaluating carbon redistribution during glucose-citrate cofermentation by Lactococcus lactis Mohamed Mahmoud Emmanuel Gentil and Richard J. Robins Groupe de Fractionnement Isotopique de Métabolismes Laboratoire d Analyse Isotopique et Electrochimique de Métabolismes Universite de Nantes France The cometabolism of citrate and glucose by growing Lactococcus lactis ssp. lactis bv. diacetylactis was studied using a natural-abundance stable isotope technique. By a judicious choice of substrates differing slightly in their 13C 12C ratios the simultaneous metabolism of citrate and glucose to a range of compounds was analysed. These endproducts include lactate acetate formate diacetyl and acetoin. All these products have pyruvate as a common intermediate. With the objective of estimating the degree to which glucose and citrate metabolism through pyruvate may be differentially regulated the Ỗ13C values of the products accumulated over a wide range of concentrations of citrate and glucose were compared. It was found that whereas the relative accumulation of different products responds to both the substrate concentration and the ratio between the substrates the Ỗ13C values of the products primarily reflect the availability of the two substrates over the entire range examined. It can be concluded that in actively growing L. lactis the maintenance of pyruvate homeostasis takes precedence over the redox status of the cells as a regulatory factor. Keywords carbon balance isotope ratio mass spectrometry lactic acid bacteria metabolic regulation pyruvate. A range of simple sugars can be catabolized anaerobically by Lactococcus lactis and other lactic acid bacteria LAB in order to obtain energy for growth. Central to this metabolism is the C3 compound pyruvate 1 . This metabolite forms the link between the essentially oxidative reactions

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