Mitochondrial Oxidase Systems in Neurospora

Author: Eakin, Richard Timothy

Year: 1968

Degree: Dissertation (Ph.D.)

Advisor: Mitchell, Herschel K.

Committee Member: Unknown, Unknown

Option: Biochemistry; Chemistry

DOI: 10.7907/YPY7-V492

Abstract

Mitochondrial oxidase systems of Neurospora crassa were investigated with respect to their mechanisms of electron transport and their relationships to respiratory metabolism.

A mitochondrial oxidase system able to utilize dihydroorotic acid as a primary substrate was found and characterized. Another substrate for this system was isolated from yeast extract and identified as 5-N-methylformamido-L-dihydroorotic acid. This system was found to occur in both wildtype and poky, a respiratory mutant. No linkage to the cytochrome chain or to oxidative phosphorylation could be detected.

A succinate oxidase system and NADH oxidase system independent of cytochromes b,a, and a3 were found to occur in both wildtype and in the poky mutant. The system was partially characterized using the poky mutant, which is deficient in cytochromes b,a and a3. It was found that this oxidase system was a part of respiratory metabolism and was linked to oxidative phosphorylation.

Mechanisms of electron transport in these oxidase systems are discussed and models presented.

Possible biological origins and the biological significance of 5 N-methylformamidodihydroorotic acid are also discussed.

The development of poky and wildtype mitochondria during the growth cycle were studied and compared. Differences in morphology were detected using electron microscopy and differences in cytochrome content were detected by absorption spectroscopy. The relationships between the oxidase systems and mitochondrial development are discussed.

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