THR246 mutations decrease substrate inhibition in lactate dehydrogenase.
Threonine 246 in Bacillus stearothermophilus L-lactate dehydrogenase has been changed to valine, serine, and alanine by site-directed mutagenesis. Kinetic analyses show a decrease in substrate inhibition for pyruvate reduction with the T246S mutant and virtual elimination of substrate inhibition for the T246A and T246V mutants. The results indicate that the absence of substrate inhibition in the 246A/V-catalyzed reactions is due to the elimination of a key hydrogen bond between the hydroxyl group of threonine and pyruvate in the wild-type complex that is an important contributor in the formation of the abortive enzyme-NAD(+)-pyruvate complex responsible for substrate inhibition.
Sakowicz
R
R
Department of Molecular and Medical Genetics, University of Toronto, Ontario, Canada.
Kallwass
H
H
Parris
W
W
Gold
M
M
Jones
J B
JB
D004926:Escherichia coli / Q000235:genetics; D001411:Geobacillus stearothermophilus / Q000201:enzymology*; D006706:Homeostasis; D007700:Kinetics; D007770:L-Lactate Dehydrogenase / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D008433:Mathematics; D016297:Mutagenesis, Site-Directed; D011773:Pyruvates / Q000494:pharmacology*; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D013912:Threonine
D011773:Pyruvates; D011994:Recombinant Proteins; D013912:Threonine; D007770:L-Lactate Dehydrogenase