Plant Physiol. Journal of Pharmacology and Experimental Therapeutics
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Plant Physiology 53:167-170 (1974)
© 1974 American Society of Plant Biologists

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Articles

Enzymes Related to Lactate Metabolism in Green Algae and Lower Land Plants 1

Peter J. Gruber2, Sue Ellen Frederick2 and N. E. Tolbert

a Department of Biochemistry Michigan State University, East Lansing, Michigan 48823

Cell-free extracts of Chlorella pyrenoidosa contained two enzymes capable of oxidizing D-lactate; these were glycolate dehydrogenase and NAD+-dependent D-lactate dehydrogenase. The two enzymes could be distinguished by differential centrifugation, glycolate dehydrogenase being largely particulate and NAD+-D-lactate dehydrogenase being soluble. The reduction of pyruvate by NADH proceeded more rapidly than the reverse reaction, and the apparent Michaelis constants for pyruvate and NADH were lower than for D-lactate and NAD+. These data indicated that under physiological conditions, the NAD+-linked D-lactate dehydrogenase probably functions to produce D-lactate from pyruvate.

Lactate dehydrogenase activity dependent on NAD+ was found in a number of other green algae and in the green tissues of a few lower land plants. When present in species which contain glycolate oxidase rather than glycolate dehydrogenase, the enzyme was specific for L-lactate rather than D-lactate. A cyclic system revolving around the production and utilization of D-lactate in some species and L-lactate in certain others is proposed.

2 Present address: Department of Biological Sciences, Mount Holyoke College, South Hadley, Mass. 01075.

1 This research was supported in part by National Science Foundation Grant GB-32040X and by a National Science Foundation Postdoctoral Fellowship to P. J. G. It is published as Journal Article No. 6466 of the Michigan Agricultural Experiment Station.






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