The second respiratory chain of Candida parapsilosis: a comprehensive study.
The yeast C. parapsilosis CBS7157 is strictly dependent on oxidative metabolism for growth since it lacks a fermentative pathway. It is nevertheless able to grow on high glucose concentrations and also on a glycerol medium supplemented with antimycin A or drugs acting at the level of mitochondrial protein synthesis. Besides its normal respiratory chain C. parapsilosis develops a second electron transfer chain antimycin A-insensitive which allows the oxidation of cytoplasmic NAD(P)H resulting from glycolytic and hexose monophosphate pathways functioning through a route different from the NADH-coenzyme Q oxidoreductase described in S. cerevisiae or from the alternative pathways described in numerous plants and microorganisms. The second respiratory chain of C. parapsilosis involves 2 dehydrogenases specific for NADH and NADPH respectively, which are amytal and mersalyl sensitive and located on the outer face of the inner membrane. Since this antimycin A-insensitive pathway is fully inhibited by myxothiazol, it was hypothesized that electrons are transferred to a quinone pool that is different from the classical coenzyme Q-cytochrome b cycle. Two inhibitory sites were evidenced with myxothiazol, one related to the classical pathway, the other to the second pathway and thus, the second quinone pool could bind to a Q-binding protein at a specific site. Elimination of this second pool leads to a fully antimycin A-sensitive NADH oxidation, whereas its reincorporation in mitochondria allows recovery of an antimycin A-insensitive, myxothiazol sensitive NADH oxidation. The third step in this second respiratory chain involves a specific pool of cytochrome c which can deliver electrons either to a third phosphorylation site or to an alternative oxidase, cytochrome 590. This cytochrome is inhibited by high cyanide concentrations and salicylhydroxamates.
Guerin
M
M
Institut de Biochimie Cellulaire et Neurochimie du CNRS, Université de Bordeaux, France.
Camougrand
N
N
Caubet
R
R
Zniber
S
S
Velours
G
G
Manon
S
S
Guelin
E
E
Cheyrou
A
A
D002175:Candida / Q000502:physiology*; D003580:Cytochromes / Q000378:metabolism; D004352:Drug Resistance, Microbial; D004579:Electron Transport; D008928:Mitochondria / Q000378:metabolism; D009249:NADP / Q000378:metabolism*; D010766:Phosphorylation; D012441:Saccharomyces cerevisiae / Q000502:physiology
D003580:Cytochromes; D009249:NADP