Abstract
Triosephosphate isomerase (TPI), which catalyses the conversion of dihydroxyacetone phosphate (DHAP) to glyceraldehyde-3-phosphate (G3P), was studied for its control on glycolysis and mixed acid production in L. lactis subspecies lactis IL1403 and L. lactis subspecies cremoris MG1363. Strains in which the TPI activity was modulated from 3%-225% (IL1403) or 13%-103% (MG1363) of the wild-type level were constructed by changing the expression of the tpiA gene. The enzyme was found to be present in high excess in the wild-type cells and 10% TPI activity still supported more than 70% of the wild-type glycolytic flux in both strains. Homolactic product formation was preserved throughout the range of TPI activities studied, although a slight increase in the amount of acetate and formate production was observed in the strains with strongly reduced TPI activity for both IL1403 and MG1363. The upstream metabolites glucose-6-phosphate, fructose-1,6-bisphosphate and DHAP in the IL1403 derivatives were essentially unchanged for TPI activities from 26% to 225%. At a TPI activity of 3%, the level of DHAP increased four times. The finding that an increased level of DHAP coincides with an increase in formate production is surprising and indicates that pyruvate formate lyase is not inhibited by DHAP under these conditions.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.