FEBS Letters | |
Histidine 64 is not required for high CO2 hydration activity of human carbonic anhydrase II | |
Behravan, Gity1  Wallgren, Katarina1  Sandström, Jan1  Liang, Zhi-wei1  Forsman, Cecilia1  Jonsson, Bengt-Harald1  Lindskog, Sven1  Ren, Xilin1  | |
[1] Department of Biochemistry, University of Umeå, S-901 87 Umeå, Sweden | |
关键词: Carbonic anhydrase; Site-directed mutagenesis; Proton transfer; Catalytic mechanism; | |
DOI : 10.1016/0014-5793(88)81156-6 | |
学科分类:生物化学/生物物理 | |
来源: John Wiley & Sons Ltd. | |
【 摘 要 】
To test the hypothesis that histidine 64 in carbonic anhydrase II has a crucial role as a ‘proton shuttle group’ during catalysis of CO2-HCO− 3 interconversion, this residue was replaced by lysine, glutamine, glutamic acid and alanine by site-directed mutagenesis. All these variants turned out to have high CO2 hydration activities. The k cat values at pH 8.8 and 25°C were only reduced by 1.5–3.5-fold compared to the unmodified enzyme. These results show that intramolecular proton transfer via His 64 is not a dominating pathway in the catalytic reaction. The variants also catalyze the hydrolysis of 4-nitrophenyl acetate. The pK a values for the activity-controlling group are between 6.8 and 7.0 for all studied forms of the enzyme except the Glu 64 variant which shows a complex pH dependence with the major pK a shifted to 8.4
【 授权许可】
Unknown
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