Diffusion limited component of mitochondrial F1-ATPase |
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| Affiliation: | 1. Department of Cardiology, the First Affiliated Hospital, Harbin Medical University, Harbin 150001, China;2. NHC Key Laboratory of Cell Translation, Harbin Medical University, Heilongjiang 150001, China;3. Key Laboratory of Hepatosplenic Surgery, Harbin Medical University, Ministry of Education, Harbin 150001, China;4. Key Laboratory of Cardiac Diseases and Heart Failure, Harbin Medical University, Harbin 150001, China;5. Heilongjiang Key Laboratory for Metabolic Disorder & Cancer Related Cardiovascular Diseases, Harbin 150081, China;6. Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Harbin, China |
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| Abstract: | - 1.1. The possibility that the rate of ATP hydrolysis by F1-ATPase approaches the diffusion-controlled limits was investigated by measuring the values of kcat and kl (kcat/Km) as a function of increasing viscosity.
- 2.2. The values of kcat/Km decrease significantly with increasing viscosity; further such decrease was lower when F1-ATPase hydrolyzed poor substrate such as Ca- and Mg-ITP or when the hydrolysis rates were measured at temperatures below 20°C.
- 3.3. Viscosity also decreases cat, but only at high concentrations of viscosogenic agents.
- 4.4. These results suggest that ATP hydrolysis is at least partly diffusion-controlled, although a general non-specific perturbation in the enzyme structure is also effected by viscosity.
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