A method is described for preparation of a microsomal fraction from tomato fruits at various stages of ripeness. Electron microscopic examination of the membrane fractions was performed. The membrane preparation utilized molecular oxygen in the presence o f NADH. This utilization was increased when cytochrome c was added, and cytochrome c enhanced the disappearance of NADH. Cytochrome c reduction was approximately equal to the loss of NADH. Cytochrome c reductase activity was not affected by stage o f ripeness. Cytochrome c enhanced both 0 2 uptake and NADH utilization by the tomato microsomes. Monophasic Arrhenius plots were observed for oxygen utilization b y the microsomal fractions i n the presence or absence o f cytochrome c.

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