Kinetics of activation of L-lactate dehydrogenase from Streptococcus lactis by fructose 1,6-bisphosphate.
A lag is observed before the steady state during pyruvate reduction catalysed by lactate dehydrogenase from Streptococcus lactis. The lag is abolished by preincubation of enzyme with the activator fructose 1,6-bisphosphate before mixing with the substrates. The rate constants for the lag phase showed a linear dependence on fructose-1,6-bisphosphate concentration, with a second-order rate constant of 2.0 X 10(4) M-1 s-1, but were independent of enzyme concentration. Binding of fructose 1,6-bisphosphate produces a decrease in the protein fluorescence of the enzyme. The second-order rate constant for the fluorescence change is twice that for the lag in pyruvate reduction. The results suggest that binding of fructose 1,6-bisphosphate induces a conformational change in the enzyme, producing a form with reduced protein fluorescence and increased activity towards pyruvate reduction.
D055598:Chemical Phenomena; D002621:Chemistry; D004789:Enzyme Activation / Q000187:drug effects; D005635:Fructosediphosphates / Q000494:pharmacology*; D006598:Hexosediphosphates / Q000494:pharmacology*; D007700:Kinetics; D007770:L-Lactate Dehydrogenase / Q000378:metabolism*; D013294:Lactococcus lactis / Q000201:enzymology*; D008433:Mathematics; D008956:Models, Chemical; D011485:Protein Binding; D013050:Spectrometry, Fluorescence; D013053:Spectrophotometry
D005635:Fructosediphosphates; D006598:Hexosediphosphates; D007770:L-Lactate Dehydrogenase; C029063:fructose-1,6-diphosphate