Studies on the effects of Al(III) on the lactate dehydrogenase activity by differential pulse voltammetry

In this paper, differential-pulse voltammetry (DPV) was applied to study the effects of aluminum (Al(III)) on the lactate dehydrogenase (LDH) activity, KmNADH and νmax in the enzyme promoting catalytic reaction of “Pyruvate+NADH+H+⇄LDHLactate+NAD+” by monitoring DPV reduction current of NAD+. The changes of Al's influence on the LDH activities caused by the concentration of LDH, pH, temperature as well as Al speciation including Al hydroxide (Al-OH), Al fluoride (Al-F) and organically complexing Al (Al-Org) compounds have been investigated. The results showed that the effects of Al on the LDH activity exhibited two kinds of behaviors under different conditions, i.e. inhibitory effects or slightly increased LDH activity at low concentrations and inhibited at high concentrations. To analyze the values of KmNADH and νmax of LDH reaction system in the absence and presence of 0.04 mmol/L Al(III), it was found that the types of the inhibition of Al(III) varied with experimental conditions. The comparisons of effects of Al(III) with Pb(II), Cd(II) and Cr(III) on the LDH activities were also inspected.