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Abstract:
INTRODUCTION
Quinol:fumarate reductases (QFR) and succinate:quinone reductases (SQR) catalyze the reduction of fumarate to succinate with concomitant oxidation of hydroquinone (quinol) to quinone, as well as the reverse reaction. SQR (respiratory complex II) is involved in aerobic metabolism as part of the citric acid cycle and the aerobic respiratory chain. QFR is involved in anaerobic respiration with fumarate as the terminal electron acceptor (Kröger, 1978; Kröger et al., 1992), and it is part of the electron transport chain catalyzing the oxidation of various donor substrates (e.g., NADH, H2 or formate) by fumarate. These reactions are coupled to ADP phosphorylation via an electrochemical proton potential.
