Intracellular Localization of Glycolate Dehydrogenase in a Blue-Green Alga

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Abstract
Glycolate dehydrogenase activity was detected in cell-free extracts of Oscillatoria sp. prepared by osmotic lysis of spheroplasts in 0.05 M potassium phosphate buffer, pH 7.5, containing 0.3 M mannitol. Most of the enzyme activity was found in a particulate fraction and localized in the photosynthetic lamellae after centrifugation in a discontinuous sucrose density gradient. Enzyme activity was detected in this fraction both in the presence and absence of the artificial electron acceptor 2,6-dichlorophenolindophenol (DPIP) and a low rate of O2 uptake was detected in this lamellar fraction. Activity was lost from the lamellar fraction by repeated washing or by treatment with 0.005% Triton X-100 and the solubilized enzyme activity was DPIP-dependent. Both glycolate dehydrogenase and its natural electron acceptor apparently are bound to the photosynthetic lamellae in vivo. In contrast, catalase activity was found in the soluble cytoplasmic fraction.