Removal of substrate inhibition in a lactate dehydrogenase from human muscle by a single residue change.
High concentrations of ketoacid substrates inhibit most natural hydroxyacid dehydrogenases due to the formation of an abortive enzyme-NAD+-ketoacid complex. It was postulated that this substrate inhibition could be eliminated from lactate dehydrogenases if the rate of NAD+ dissociation could be increased. An analysis of the crystal structure of mammalian LDHs showed that the amide of the nicotinamide cofactor formed a water-bridged hydrogen bond to S163. The LDH of Plasmodium falciparum is not inhibited by its substrate and, uniquely, in this enzyme the serine is replaced by a leucine. In the S163L mutant of human LDH-M4 pyruvate inhibition is, indeed, abolished and the enzyme retains high activity. However, the major contribution to this effect comes from a weakening of the interaction of pyruvate with the enzyme-coenzyme complex.
Eszes
C M
CM
Molecular Recognition Centre and Department of Biochemistry, School of Medical Sciences, University Walk, Bristol, UK.
Sessions
R B
RB
Clarke
A R
AR
Moreton
K M
KM
Holbrook
J J
JJ
D006801:Humans; D007700:Kinetics; D007770:L-Lactate Dehydrogenase / Q000235:genetics / Q000378:metabolism*; D009132:Muscles / Q000201:enzymology*; D016297:Mutagenesis, Site-Directed; D009243:NAD / Q000037:antagonists & inhibitors / Q000378:metabolism; D011773:Pyruvates / Q000037:antagonists & inhibitors / Q000378:metabolism; D013379:Substrate Specificity
D011773:Pyruvates; D009243:NAD; D007770:L-Lactate Dehydrogenase