Structural and regulatory studies on the ribulose bisphosphate carboxylase-oxygenase of Anabaena cylindrica

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Ribulose 1,5-bisphosphate (RuBP) carboxylase-oxygenase from the cyanobacterium Anabaena cylindrica has been purified to homogeneity by the criterion of polyacrylamide gel electrophoresis and shown to consist of two types of subunits of molecular weights 51K (large) and 12K (small). The enzyme is of the higher plant type and probably consists of 8 large plus small subunits. Isoelectric focusing of the S-carboxymethylated protein in 8 M urea revealed a profile of consisting of 3 major polypeptides plus 1 minor polypeptide. Some characteristics of the carboxylase and oxygenase reactions were studied using simultaneous measurements of both activities. Pyridoxal 5'-phosphate inhibited both activities equally. Neither the carboxylase nor oxygenase reaction was affected by glutamate (5 mM), although 6-phosphogluconate and fructose 1,6-bisphosphate inhibited both reactions. RuBP oxygenase was more sensitive to 6-phosphogluconate (0.5 and 1.0 mM) than RuBP carboxylase. Marked changes in the oxygenase to carboxylase activity ratio of the purified enzyme were effected by homologous antiserum (which preferentially inhibited carboxylation).
日本植物生理学会の論文