Anaerobic Formation of d-Lactate and Partial Purification and Characterization of a Pyruvate Reductase from Chlamydomonas reinhardtii

Factors Affecting Development of Peroxisomes and Glycolate Metabolism among Algae of Different Evolutionary Lines of the Prasinophyceae

“…Thus, the potential for D-lactate synthesis and oxidation was measured in this evolutionary line of algae for association with the appearance of the peroxisomal system. Considerable amounts of pyruvate reductase activity for D-lactate formation was found in the unicellular members of Prasinophyceae, such as Pyvamimonas and Pedinomonas, and of Chlorophyceae, such as Cklamydomonas artd Dunaliella (Husic and Tolbert, 1985a), whereas much less activity was found in the filamentous Mougeotia algae with leaf-type peroxisomes and glycolate oxidase, which oxidize L-lactate (Table 111). Thus, the filamentous algae of this line more closely resemble higher plants than unicellular algae with regard to lactate and glycolate oxidation.…”

“…nase in unicellular green algae or in cyanobacteria to further oxidize a11 of the glycolate (Tolbert et al, 1970;Husic et al, 1987;Husic and Tolbert, 1985a;Kehlenbeck, 1994). Unicellular green algae also possess an active pyruvate reductase with which to synthesize D-lactate, which could be used as a substrate by glycolate dehydrogenase Tolbert, 1985a, 1992;Stabenau et al, 1989;Winkler and Stabenau, 1992).…”

“…The homogenate was centrifuged at 27, OOOg for 15 min, and the supernatant was used for the enzyme assay. The pyruvate reductase activity was measured by following the oxidation of NADH upon the addition of pyruvate (Husic and Tolbert, 1985a). The assay mixture in 1 mL contained 125 mM potassium phosphate buffer (pH 7.0), 80 p~ NADH, 2 mM pyruvate, and 100 pL of enzyme or extract.…”

Inhibition of glycolate and D-lactate metabolism in a Chlamydomonas reinhardtii mutant deficient in mitochondrial respiration

“…Aliquots of photosynthesizing cells were added directly to methanol to terminate reactions without centrifugation of cells into a tightly packed pellet. This procedure avoided the introduction of anaerobic conditions, during which up to 50% of the 14C could accumulate in D-lactate (9). Under these aerobic photosynthetic conditions, significant amounts of [14C]lactate did not accumulate, even after 5 min of labeling dk97 cells with H14CO-in either the presence or absence of SHAM (Table 3).…”

“…It was known from previous work that D-lactate accumulates during short time periods of anaerobiosis in Chlamydomonas (9) and in other unicellular algae (10,11). We provide evidence here that, in Chlamydomonas, oxidation of anaerobically produced D-lactate is dependent on aerobic conditions.…”