Ribulose-1, 5-Bisphosphate Carboxylase/Oxygenase from an Ammonia-Oxidizing Bacterium, Nitrosomonas sp. K1 : purification and Properties

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The ammonia-oxidizing chemoautotrophic Nitrosomonas sp. strain K1 exhibited marked ribulose-1, 5-bisphosphate carboxylase (RubisCO) activity. The RubisCO [EC 4.1.1.39] was purified as an electrophoretically homogeneous protein. The molecular mass of the enzyme was estimated to be about 460 kDa by gel filtration, and it consists of two subunits [large (L): 52.2 kDa; small (S): 13.3 kDa] as demonstrated by SDS PAGE. This confirmed that the enzyme has an L_8S_8 structure. The K_m values of the enzyme for RuBP, NaHCO_3, and Mg^<2+> were estimated to be 0.112, 0.415, and 1.063 mM, respectively. The optimum pH and temperature for its activity were approximately 7.0 and 45℃. The enzyme was stable up to 45℃ and in a pH range from 7.0-9.0 (4℃, 48 h). The enzyme activity was inhibited by Cu^<2+> Hg^<2+> N-ethylmaleimide, p-chloromercuribenzoate, and SDS (0.1 mM). The activity was also inhibited by ammonium sulfate at high concentrations (38-303 mM) but the stability of the enzyme showed no inhibition at the same ammonium sulfate concentrations. The N-terminal amino acid sequences of the large and small subunits are AIKTYQAGVKEYRQTYW QPDYVPL and AIQAYHLTKKYETFSYLPQM, respectively.
社団法人日本生物工学会の論文
2000-10-25