Analytical Sciences

Integrated Rate Equation Considering Product Inhibition and Its Application to Kinetic Assay of Serum Ethanol

Fei LIAO,* Li-na ZHAO,* Yun-sheng ZHAO,* Jia TAO,* and Yuping ZUO**

*Laboratory of Bioinformatics & Molecular Engineering, Chongqing Key Laboratory of Biochemistry & Molecular Pharmacology, College of Pharmaceutical Sciences, Chongqing Medical University, Chongqing 400016, People's Republic of China
**Department of Biochemistry & Molecular Biology, College of Basic Medical Sciences, Chongqing Medical University, Chongqing 400016, People's Republic of China

Kinetic assay of serum ethanol was investigated by predicting maximal product absorbance at 340 nm (A_mk) through fitting to the yeast alcohol dehydrogenase reaction curve with the integrated rate equation, taking into account product inhibition in the presence of semicarbazide. Predicted A_mk linearly responded to the preset constant of steady-state concentration of acetaldehyde (C_ald). An exponential correlation function was established between desired C_ald and putative A_mk for authentic ethanol. For unknown samples, iterative fitting to reaction curve till preset constant C_ald and resultant A_mk satisfied this exponential correlation function yielded A_mk with variation coefficient <4.3%. Variations in enzyme activity, data range and kinetic parameters showed negligible effects. The recovery was consistent to 100% with resistance to methanol and isopropanol. The upper limit of linear response for A_mk was about 40 times of the lower limit. These results indicated that this kinetic method was reliable for serum ethanol assays with obvious advantages.

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