Ribulose-1,5-diphosphate carboxylase of Chromatium strain D

概要

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RuDP carboxylase isolated from autotrophically grown cells of photosynthetic sulfur bacterium, Chromatium strain D, was partially purified by (NH_4)_2SO_4 precipitation and Scphadex G-200 gel filtration. The molecular size of the bacterial RuDP carboxylase was found to be large, analogous to that of the plant enzyme, in agreement with results of previous workers. Sucrose density gradient centrifugation showed the S_<rel%gt; to be approximately 18; the omission of Mg^<++> caused no dissociation of the enzyme molecule in its subunits. Chromatium RuDP carboxylase showed similarities to the plant enzyme in some of its kinetic properties; (a) a shift of pH optimum to the neutral side from the alkaline side on the addition of Mg^<++>, (b) deviation of the substrate concentration (NaHCO_3)-activity relationship from the MICHAELIS formula and (c) a marked stimulative effect of Mg^<++>. A unique sigmoidal saturation curve of the to RuDP, which had been detected in Rhodospirillum rubrum and Rhodopseudomonas spheroides RuDP carboxylase in the absence of Mg^<++>, was not found. Another characteristic feature of Chromatium RuDP carboxylase is its partial immunological response to the rabbit anti-spinach RuDP carboxylase serum as detected by the inhibition of the carboxylation reaction due to the antibody-antigen reaction.
日本植物生理学会の論文