Metabolism of Pyruvate by Starved Cells of Chlorella elipsoida

Abstract

The metabolism and function of the organic acids of the tricarboxylic acid (TCA) cycle in plants and microorganisms is not clearly understood. Evidence from the effects of inhibitors, the incorporation of radioactivity from specifically labeled acids, and the isolation of the acid intermediates and the active enzymes (3,4,11,24,26,30)

Influence of Glucose & Light on Pyruvate Metabolism by Starved Cells of Chlorella elipsoida

“…Cells of Chlorella elipsoida Gerneck (culture supplied by Prof. A. Pirson) were grown as previously described (22) starved overnight in distilled water, centrifuged, washed, and placed in WVarburg flasks with 0.017 M phosphate buffer (pH 5.6). At the end of the experiment (2-2y2 hr) the cells were extracted first with hot water (H.W.E.…”

“…a material which runs with the front in the butanolpropionic acid-water solution (fats). The killing procedure, estimation of radioactivity, and identification of the components within each fraction have already been described (22). (16).…”

“…In Chlorella cells the oxidation of glucose proceeds by the glycolytic and pentosephosphate pathways to phosphoglyceraldehyde an(l pyruvate (12); the resulting pyruvate appears to be oxidized by the tricarboxylic acid (TCA) cycle (22). Since the respiration in plant cells and microorganisms is geared primarily to the synthetic requirements, a delicate balance must be established between those reactions which require carbon skeletons and those which produce the energy and reducing power necessary to drive the synthesis of new materials.…”

“…With glucose as a substrate there is a high rate of respiration until all the substrate is gone (8) showing that such a balance is achieved. On the other hand, the increased respiration induced by pyruvate falls before the substrate is completely utilized (22). If the rate of uptake of pyruvate from the medium is limited by its ability to support synthetic reactions, then the addition of either glucose or light partially overcomes the deficiency (22).…”

“…On the other hand, the increased respiration induced by pyruvate falls before the substrate is completely utilized (22). If the rate of uptake of pyruvate from the medium is limited by its ability to support synthetic reactions, then the addition of either glucose or light partially overcomes the deficiency (22). Indeed the inability of pyruvate to support the assimilation of NH3 (10) or growth (6) indicates that the acids of the TCA cycle alone cannot promote the synthesis of proteins.…”