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Nature of the effect of adenosine 5'-monophosphate on the cyanide-insensitive respiration in mitochondria of Moniliella tomentosa.

ABSTRACT: The alternative oxidase of Moniliella tomentosa mitochondria is stimulated by 5'-AMP. This effect may be masked, depending on the isolation procedure of the mitochondria. The preparation of submitochondrial particles results in the expression of the 5'-AMP effect. Two more methods are now described to reveal the 5'-AMP effect whenever it would be masked: (1) switching on the myokinase activity of the mitochondria to deplete them of endogenous 5'-AMP; (2) using detergents (sodium dodecyl sulphate, sodium deoxycholate) in a controlled detergent:protein ratio, or chloroform. The alternative oxidase of detergent-solubilized mitochondria was somewhat less selective towards nucleotides than were intact mitochondria. The effect of nucleotides on quinol oxidation by mitochondrial preparations and on quinol autoxidation was also studied. Mitochondrial oxidation of succinate by the alternative oxidase and autoxidation of quinols behaved similarly in the presence of certain nucleotides. Both reactions were stimulated. Both reactions were also inhibited by salicylhydroxamic acid. These effects on quinol oxidation disappeared when bovine serum albumin or mitochondrial proteins were present. From the results obtained it is not possible to exclude quinol autoxidation as a final step of the alternative oxidase.

SUBMITTER: Vanderleyden J

PROVIDER: S-EPMC1161532 | biostudies-other | 1980 Jan

REPOSITORIES: biostudies-other

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Characterization of cyanide-insensitive respiration in mitochondria and submitochondrial particles of Moniliella tomentosa.

Project description:Mitochondria and submitochondrial particles of the osmophilic yeast-like fungus Moniliella tomentosa may respire by means of two pathways: a normal cytochrome pathway, sensitive to cyanide and antimycin A, and an alternative pathway, which is insensitive to these inhibitors but is specifically inhibited by salicylhydroxamic acid. The affinities of both oxidases for succinate and NADH as substrates, for O(2) as terminal electron acceptor, and for AMP as stimulator of the alternative oxidase were determined. 1. Submitochondrial particles of M. tomentosa may also respire by means of a cyanide-sensitive and/or cyanide-insensitive system. 2. The activities of both oxidases as compared with the total activity are roughly the same in submitochondrial particles as in the original mitochondria. 3. The terminal oxidase of the cyanide-insensitive pathway requires a 10-fold higher O(2) concentration for saturation than does cytochrome c oxidase. 4. The apparent K(m) for succinate is about 3 times higher for the alternative than for the normal oxidase when measured in mitochondria, and 4-10 times higher when measured in submitochondrial particles. The apparent K(m) for NADH is roughly the same for both oxidases. 5. The apparent K(m) values of both oxidases for succinate are always lower in submitochondrial particles than in mitochondria. 6. The apparent K(m) for AMP, acting as a stimulator of the alternative oxidase, is the same (25mum) in mitochondria as in sub-mitochondrial particles. These results are discussed in the light of the structure and localization of the components of the alternative oxidase.

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Identification of the quinone species in cyanide-sensitive and cyanide-insensitive mitochondria of Moniliella tomentosa.

Project description:Moniliella tomentosa was investigated for the presence of different quinones that might be involved in the cyanide-sensitive and/or cyanide-insensitive electron-transport pathways. The naturally occurring quinone in Moniliella tomentosa was found to be ubiquinone-45. Other quinone species could not be detected. The concentration of ubiquinone-45 in mitochondria is not related to the presence or absence of the alternative oxidase activity.

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Cyanide Insensitive Oxidase Confers Hydrogen Sulfide and Nitric Oxide Tolerance to <i>Pseudomonas aeruginosa</i> Aerobic Respiration.

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