Parameter estimation for models of ligninolytic and cellulolytic enzyme kinetics

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• 作者：Gangsheng Wang^a ; ^{wangg@ornl.gov} ; Wilfred M. Post^a ; Melanie A. Mayes^a ; Joshua T. Frerichs^b ; Jagadamma Sindhu^a
• 关键词：Cellulases ; Enzyme kinetics ; Half-saturation constant ; Ligninases ; Specific enzyme activity
• 刊名：Soil Biology & Biochemistry
• 出版年：2012
• 期刊代码：96_00380717
• 类别：abs
• 出版时间：May, 2012
• 卷：48
• 期：Complete
• 页码：28-38
• 文件大小：669 K

摘要

While soil enzymes have been explicitly included in the soil organic carbon (SOC) decomposition models, there is a serious lack of suitable data for model parameterization. This study provides well-documented enzymatic parameters for application in enzyme-driven SOC decomposition models from a compilation and analysis of published measurements. In particular, we developed appropriate kinetic parameters for five typical ligninolytic and cellulolytic enzymes (尾-glucosidase, cellobiohydrolase, endo-glucanase, peroxidase, and phenol oxidase). The kinetic parameters included the maximum specific enzyme activity (V_max) and half-saturation constant (K_m) in the Michaelis-Menten equation. The activation energy (Ea) and the pH optimum and sensitivity (pH_opt and pH_sen) were also analyzed. pH_sen was estimated by fitting an exponential-quadratic function. The V_max values, often presented in different units under various measurement conditions, were converted into the same units at a reference temperature (20聽掳C) and pH_opt. Major conclusions are: (i) Both V_max and K_m were log-normal distributed, with no significant difference in V_max exhibited between enzymes originating from bacteria or fungi. (ii)聽No significant difference in V_max was found between cellulases and ligninases; however, there was significant difference in K_m between them. (iii) Ligninases had higher Ea values and lower pH_opt than cellulases; average ratio of pH_sen to pH_opt ranged 0.3-0.4 for the five enzymes, which means that an increase or decrease of 1.1-1.7 pH units from pH_opt would reduce V_max by 50%. (iv) Our analysis indicated that the V_max values from lab measurements with purified enzymes were 1-2 orders of magnitude higher than those for use in SOC decomposition models under field conditions.