Respiratory chain network in mitochondria of Candida parapsilosis: ADP/O appraisal of the multiple electron pathways

In this study we demonstrated that mitochondria. of Candida parapsilosis co ntain a constitutive ubiquinol alternative oxidase (AOX) in addition to a c lassical respiratory chain (CRC) and a parallel respiratory chain (PAR) bot h terminating by two different cytochrome c oxidases. The C. parapsilosis A OX is characterized by a fungi-type regulation by GMP (as a stimulator) and linoleic acid (as an inhibitor). Inhibitor screening of the respiratory ne twork by the ADP/O ratio and state 3 respiration determinations showed that (i) oxygen can be reduced by the three terminal oxidases through four path s implying one bypass between CRC and PAR and (ii) the sum of CRC, AOX and PAR capacities is higher than the overall respiration (no additivity) and t hat their engagement could be progressive according to the redox state of u biquinone, i.e. first cytochrome pathway, then AOX and finally PAR. (C) 200 1 Published by Elsevier Science B.V. on behalf of the Federation of Europea n Biochemical Societies.