Enhancing effects of CO2 on chloroplast regeneration in glucose-bleached cells of Chlorella protothecoides II. Role of carbamylphosphate in chloroplast regeneration

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Abstract
Levels of the activities of glutamine-dependent carbamylphosphate synthetase, ornithine-and aspartate-transcabamylase and phosphoenolpyruvate carboxylase were followed in greening cells of Chlorella prolothecoides. Among the enzymes examined the activity of carbamylphosphate synthetase was extremely low, especially at the early phase of greening. Arginine (but not ornithine or aspartate), when administered to algal cells at the 24th hour of greening, stimulated the syntheses of RNA, protein and chlorophyll in the subsequent period. It also affected the metabolic pathway of the 14CO2 supplied simultaneously with arginine in the presence of CMU. Arginine produced a decreased incorporation of 14C into protein and an increased incorporation into nucleic acid. The mechanism of the action of CO2 on chloroplast regeneration is discussed. We concluded that chloroplast regeneration in glucose-bleached cells is limited by the synthesis of carbamylphosphate, especially in the early phase of greening.