Application of reduced graphene oxide and carbon nanotube modified electrodes for measuring the enzymatic activity of alcohol dehydrogenase

► The effects of Al3+ and nano-Al13 on the activity of the key enzyme ADH were studied. ► The ADH activity has been successfully investigated using MWNT and rGO modified electrodes. ► The study provided molecular-level information about the effect of Al(III) on ADH activity. An electrochemical method was developed to measure the enzymatic activity of alcohol dehydrogenase (ADH) by monitoring the amount of reduced nicotinamide adenine dinucleotide (NADH) generated in the catalysed oxidation of ethanol by ADH. The concentration of NADH was determined by amperometric measurements, which recorded the oxidation current of NADH versus time on reduced graphene oxide and functionalised multi-walled carbon nanotube modified electrodes. The initial reaction rates and the apparent Michaelis constants of the enzymatic reaction were obtained in the absence and presence of Al3+ and nanometre-sized tridecameric aluminium polycationic (nano-Al13) species. The results showed that Al3+ and nano-Al13 exhibited inhibitory effect on the enzymatic activity of ADH. Fluorescence and circular dichroism spectra indicated the inhibitory effect was likely caused by the conformational changes of ADH and/or NADH induced by Al3+ and nano-Al13.