| Autor: |
E O, Maklashina, V D, Sled', A D, Vinogradov |
| Rok vydání: |
1994 |
| Předmět: |
|
| Zdroj: |
Biokhimiia (Moscow, Russia). 59(7) |
| ISSN: |
0320-9725 |
| Popis: |
Isolated Complex I exists in two forms. The active form catalyzes the rapid rotenone-sensitive, N-ethylmaleimide-insensitive NADH : Q1 reductase reaction. The inactive form is inhibited by N-ethylmaleimide and catalyzes the rotenone-sensitive ubiquinone reduction with a prominent lag phase. The inactive enzyme is transformed into its active form after rapid reduction by NADH and slow (compared with the steady-state turnover number) oxidation by quinone. The rate of activation is strongly temperature-dependent (the activation energy is 170 kJ/mol) and influenced by pH and divalent cations. The active enzyme is quite stable (hours at 0 degrees C) but it is spontaneously deactivated at high temperature (the activation energy is 245 kJ/mol). The active/inactive transition parameters are qualitatively and quantitatively similar for the isolated and membrane-bound Complex I. The extent of the isolated Complex I activation in the presence of NADH depends on the concentration of the added quinone. The concentration of quinone needed for the half-maximal activation is 10 times less than the KQ1m value in the steady-state NADH : Q1 reductase reaction. The data obtained suggest that the free energy of NADH oxidation in the respiratory chain is partly utilized to maintain the catalytically competent Complex I conformation. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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