The effect of organic acids, inhibitors and enzymes on the respiration of Chlorella

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Abstract
The effect of several enzymes, inhibitors, and adenosinetriphosphate, together with organic acids, on the rate of O2 uptake of Chlorella homogenate was studied by manometric expts. conducted in the dark. An investigation of the dehydrogenase system was also conducted by a slightly modified Thunberg technic. Cytochrome oxidase and coenzyme I, in the presence of malate and lactate, produced an increase in the rate of O2 uptake and also shortened the time of methylene blue reduction. KCN inhibited this stimulation. These effects suggest that malate and lactate are oxidized in Chlorella in the same manner as in animal tissues. Malonate did not produce an inhibition of respiration with or without succinate. This might indicate that succinic dehydrogenase is not the only possible path to fumarate formation and points toward a separate mechanism for the formation of C3 and C4 acids. The comparatively rapid oxidation of pyruvate by Chlorella in the presence of methylene blue strongly suggests that pyruvate oxidation takes place through a pyruvic-dehydrogenase system. The respiration rate of Chlorella was not affected by the addition of various amts. of adenosinetriphosphate to systems with or without organic acids. Some hydrolysis of adenosinetriphosphate was detected.