The steady-state mechanism of cytochrome c oxidase: redox interactions between metal centres.

摘要: The steady-state behaviour of isolated mammalian cytochrome c oxidase was examined by increasing the rate reduction . Under these conditions enzyme9s 605 (haem a ), 655 3 /Cu B ) and 830 (Cu A ) nm spectral features behaved as if they were at near equilibrium with (550 nm). This has implications for non-invasive tissue measurements using visible (550, nm) near-IR (830 light. oxidized species represented 655 nm band is bleached presence oxygen intermediates P F (where characterized an absorbance spectrum 607 nm relative to enzyme 580 nm enzyme) or haem Cu However, ambient levels (far above K m populations reduced very low ( centre. We present model where small anti-cooperative redox interactions occur between –Cu (steady-state potential ranges: , 212–258 mV; 254–281 227–272 mV). Contrary static measurements, in catalytic steady state there are no high centres (>300 mV). find that overall reaction correctly described classical which Michaelis intermediate ferrocytochrome –enzyme complex. oxidation this complex not sole rate-determining step. Turnover instead dependent upon electron transfer from but closely matches all times.