tailieunhanh - Báo cáo khoa học: Inhibition kinetics of catabolic dehydrogenases by elevated moieties of ATP and ADP – implication for a new regulation mechanism in Lactococcus lactis

ATP and ADP inhibit, in varying degrees, several dehydrogenases of the central carbon metabolism of Lactococcus lactisATCC 19435in vitro, . glyceraldehyde-3-phosphate dehydrogenase (GAPDH), lactate dehydroge-nase (LDH) and alcohol dehydrogenase (ADH). Here we demonstrate mixed inhibition for GAPDH and competitive inhibition for LDH and ADH by adenine nucleotides in single inhibition studies. | Inhibition kinetics of catabolic dehydrogenases by elevated moieties of ATP and ADP - implication for a new regulation mechanism in Lactococcus lactis Rong Cao Ahmad A. Zeidan Peter Radstrom and Ed W. J. van Niel Department of Applied Microbiology Lund University Sweden Keywords ADP ATP dehydrogenase Lactococcus lactis multiple inhibition kinetics Correspondence E. W. J. van Niel Department of Applied Microbiology Lund University PO Box 124 SE-221 00 Lund Sweden Fax 46 46 2224203 Tel 46 46 2220619 E-mail Received 22 September 2009 revised 18 December 2009 accepted 1 February 2010 doi ATP and ADP inhibit in varying degrees several dehydrogenases of the central carbon metabolism of Lactococcus lactis ATCC 19435 in vitro . glyceraldehyde-3-phosphate dehydrogenase GAPDH lactate dehydrogenase LDH and alcohol dehydrogenase ADH . Here we demonstrate mixed inhibition for GAPDH and competitive inhibition for LDH and ADH by adenine nucleotides in single inhibition studies. The nonlinear negative co-operativity was best modelled with Hill-type kinetics showing greater flexibility than the usual parabolic inhibition equation. Because these natural inhibitors are present simultaneously in the cytoplasm multiple inhibition kinetics was determined for each dehydrogenase. For ADH and LDH the inhibitor combinations ATP plus NAD and ADP plus NAD are indifferent to each other. Model discrimination suggested that the weak allosteric inhibition of GAPDH had no relevance when multiple inhibitors are present. Interestingly with ADH and GAPDH the combination of ATP and ADP exhibits lower dissociation constants than with either inhibitor alone. Moreover the concerted inhibition of ADH and GAPDH but not of LDH shows synergy between the two nucleotides. Similar kinetics but without synergies were found for horse liver and yeast ADHs indicating that dehydrogenases can be modulated by these nucleotides in a nonlinear manner in many .