Enzymatic properties of the lactate dehydrogenase enzyme from Plasmodium falciparum.
The lactate dehydrogenase enzyme from Plasmodium falciparum (PfLDH) is a target for antimalarial compounds owing to structural and functional differences from the human isozymes. The plasmodial enzyme possesses a five-residue insertion in the substrate-specificity loop and exhibits less marked substrate inhibition than its mammalian counterparts. Here we provide a comprehensive kinetic analysis of the enzyme by steady-state and transient kinetic methods. The mechanism deduced by product inhibition studies proves that PfLDH shares a common mechanism with the human LDHs, that of an ordered sequential bireactant system with coenzyme binding first. Transient kinetic analysis reveals that the major rate-limiting step is the closure of the substrate-specificity loop prior to hydride transfer, in line with other LDHs. The five-residue insertion in this loop markedly increases substrate specificity compared with the human muscle and heart isoforms.
Shoemark
Deborah K
DK
Department of Biochemistry, School of Medical Sciences, University of Bristol, University Walk, Clifton, Bristol, UK. deb.shoemark@bris.ac.uk
Cliff
Matthew J
MJ
Sessions
Richard B
RB
Clarke
Anthony R
AR
D000818:Animals; D003903:Deuterium / Q000378:metabolism; D015195:Drug Design; D031541:Fluorescence Resonance Energy Transfer; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D007770:L-Lactate Dehydrogenase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009243:NAD / Q000378:metabolism; D010963:Plasmodium falciparum / Q000201:enzymology*; D013379:Substrate Specificity
D009243:NAD; D003903:Deuterium; D007770:L-Lactate Dehydrogenase