| Biomedicine |
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| Kinetic analysis of γ-glutamyltransferase reaction process for measuring activity via an integration strategy at low concentrations of γ-glutamyl p-nitroaniline |
| Zhi-rong Li, Yin Liu, Xiao-lan Yang, Jun Pu, Bei-zhong Liu, Yong-hua Yuan, Yan-ling Xie, Fei Liao |
| Key Laboratory of Medical Laboratory Diagnostics of Ministry of Education, Chongqing Medical University, Chongqing 400016, China, Unit for Biotransformation and Protein Biotechnology, Chongqing Key Laboratory of Biochemical and Molecular Pharmacology, Chongqing Medical University, Chongqing 400016, China |
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Abstract At 0.12 mmol/L γ-glutamyl p-nitroaniline (GGPNA), an improved integrated method was developed for kinetic analysis of γ-glutamyltransferase (GGT) reaction process and the integration with the classical initial rate method to measure serum GGT. For the improved integrated method, an integrated rate equation, which used the predictor variable of reaction time and considered inhibitions by both GGPNA and products, was nonlinearly fit to GGT reaction processes. For the integration strategy, classical initial rates were estimated when GGPNA consumption percentages were below 50%; otherwise, maximal reaction rates of GGT were estimated by the improved integrated method and converted into initial rates according to the differential rate equation at 0.11 mmol/L GGPNA. The integration strategy was validated using optimized GGT kinetic parameters and 10-s intervals to record reaction curves within 8.0 min. By the integration strategy, there was a linear response from 0.9 to 32.0 U/L GGT, coefficients of variation were below 3.5% for GGT from 8.0 to 32.0 U/L (n=5), and GGT activities in clinical sera responded linearly to their classical initial rates at 2.00 mmol/L GGPNA with an expected slope. Therefore, the integration strategy was successful in measuring GGT at 0.12 mmol/L GGPNA.
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Received: 10 May 2010
Published: 09 March 2011
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