Ion mobility spectrometry: a valuable tool for kinetic studies in enzymology.

The inherent characteristics of IMS such as reduced measurement time, in the seconds time scale, sensitivity and selectivity make this technique an ideal methodology for enzyme reaction monitoring. The capability of IMS in the determination of enzyme kinetics and inhibition studies by the analysis of substrate depletion and/or product formation using only a few microliters of solution has been successfully demonstrated on the example of acetylcholine hydrolysis catalyzed by acetylcholinesterase (AChE) and inhibited by neostigmine and galanthamine. Michaelis-Menten and Lineweaver-Burk plots were obtained for the enzyme catalyzed reaction with and without neostigmine and galanthamine inhibition at two different inhibitor concentrations. Typical plots of competitive inhibitors were obtained agreeing well with previous results published in the literature. IMS procedure provided a limit of detection for acetylcholine in the low ppm range, a precision of 4.8% and an analysis frequency of 40s, being those analytical characteristics appropriate to perform enzyme kinetic studies. IMS offers a new and efficient tool to study enzyme reactions either as a high throughput screening tool for hit discovery and lead development for drug discovery proposes or to indirectly perform enzymological studies.