�ber Aktivit�tssteigerungen der Pyruvatkinase durch Blaulicht oder Glucose bei einer chlorophyllfreien Chlorella-Mutante

Abstract

Crude extracts of dark-kept resting cells of a chlorophyll-free, carotenoid-containing mutant of Chlorella vulgaris Beijerinck (211-11h/20) were found to convert 14.44±0.77 nmol PEP per min and mg protein into pyruvate by the action of pyruvate kinase (=PK; EC 2.7.1.40). When such cells were exposed to blue light (λ<550 nm, ∼300 μW cm(-2)) for 3 hrs the PK-activity/protein of their crude extracts rose to 21.47±1.30, i.e., it was enhanced by 43%. Poisoning with 10(-3) mol cycloheximide or with 150 μg actinomycin D/ml prevented the effect of blue light by 80-90% (Table 1). This result points to an induction of enzyme synthesis in blue light. Addition of 1% glucose in the dark resulted in an increase in PK-activity, too. Three hrs after application of glucose the PK-activity was 28.05±1.88 nmol/min and mg protein, which was 94% greater than in the control. The effect of glucose was also largely preventable by cycloheximide (10(-3) mol) or by actinomycin D (150 μg/ml) (Table 2). These results lead to the conclusion that blue light may induce the synthesis of PK by supplying free sugars at the site of enzyme synthesis. The assumption is supported by the observation that in hot water extracts of blue illuminated cells in which glucose oxidation had been poisoned by. 10(-2) mol monoiodoacetic acid there was 60% more glucose, glucose-6-phosphate, fructose-6-phosphate and sucrose detectable than in extracts of equally poisoned algae from darkness (Table 3). It is suggested that blue light activates a system for the transport of sugar out of the chloroplast, which results in the induction of respiratory enzyme synthesis and thus in enhanced respiration.

Blue‐light‐control of the uptake of amino acids and of ammonia in Chlorella mutants

“…3, Kamiya 1997). Blue light is known to enhance respiration in the same algae through starch breakdown (Kowallik and Gaffron 1966, Kamiya and Miyachi 1974, Kowallik 1982) and enhances the formation of glycolytic enzymes; phosphoenolpyruvate carboxylase (PEPC) (Kamiya and Miyachi 1975) and pyruvate kinase (PK) (Kowallik and Ruyters 1976). If glucose can induce glycolytic enzymes mentioned above and carrier systems including amino acids and nitrate, blue light might be acted at the formation of glucose through the breakdown of starch.…”

Effects of Blue Light on Enzymes

“…20 all were inhibited under such conditions. Since the latter result is different from the results for these enzymes from irradiated ChIarella cells [3,34], this finding raises new questions as to the physiological meaning of this effect.…”

“…In most cases BL-mediated changes in V m ax are considered to be indicative of protein synthesis. In addition, some experiments with protein synthesis inhibitors have been reported (e .g., [28,34 D. Both results together strongly suggest the involvement of protein synthesis in the BL control of enzymes, but proof can only come from somewhat more sophisticated techniques like immunological procedures or comparative density labeling. In fact, very recently Hundrieser and Richter [26] (Richter this Vol.)…”

Effects of Blue‐light on Pyruvate Kinase Activity During Chloroplast Development of Unicellular Green Algae*

“…yeast and beef extract . The preparation of cell suspensions and crude extracts, as well as the irradiation of the cell suspensions, were carried out as published previously (Kowallik and Ruyters, 1976;Ruyters and Kowallik, 1980). The soluble protein was measured according to Lowry rf al.…”

“…Blue-light exerts a stimulating effect on respiration and carbohydrate degradation of green algae (Kowallik, 1970;Kowallik and Schatzle, 1980). In analysing this phenomenon, Kowallik and Ruyters (1976) demonstrated an enhancement of pyruvate kinase activity in the chlorophyll-free, carotenoid-con taining mutant, No. 20, of Chlorellu oulguris.…”