Kinetic properties of lipoxygenase from desert truffle (Terfezia claveryi Chatin) ascocarps: effect of inhibitors and activators.
There is very little information available on the kinetic characteristics of fungal lipoxygenases (LOXs) because most data on the mechanism of this enzyme concern soybean LOX. In this paper, the kinetic properties of LOX from Terfezia claveryi Chatin ascocarps were studied for the first time. The enzyme did not show the "substrate aggregation-dependent activity" described for other LOXs and presented a K(m) for linoleic acid of 41 microM at pH 7.0. The effect of different inhibitors was also studied. The enzyme presented the characteristic lag phase of other LOXs, and the influence of different factors on its duration was analyzed. The lag period was reduced not only by the product of the reaction (13-HPOD) but also by 9-HPOD. Calculation of the activation constant is proposed for the first time as a useful tool for the characterization of LOX because this method makes it possible to quantify the effectiveness of different hydroperoxides as LOX activators. The activation constants obtained were 0.3 and 6.4 microM for 13- and 9-HPOD, respectively; thus, the product of the reaction was approximately 21-fold more effective than 9-HPOD as a T. claveryi LOX activator.
Pérez-Gilabert
Manuela
M
Departamento de Bioquímica y Biología Molecular-A, Facultad de Biología, Universidad de Murcia, Campus de Espinardo, E-30071 Murcia, Spain. mpg@um.es
Sánchez-Felipe
Isabel
I
Morte
Asunción
A
García-Carmona
Francisco
F
D001203:Ascomycota / Q000201:enzymology*; D004789:Enzyme Activation; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D019787:Linoleic Acid / Q000378:metabolism; D008041:Linoleic Acids / Q000494:pharmacology; D008054:Lipid Peroxides / Q000494:pharmacology; D008084:Lipoxygenase / Q000378:metabolism*; D016859:Lipoxygenase Inhibitors / Q000494:pharmacology
D008041:Linoleic Acids; D008054:Lipid Peroxides; D016859:Lipoxygenase Inhibitors; C038649:13-hydroperoxy-9,11-octadecadienoic acid; D019787:Linoleic Acid; D008084:Lipoxygenase