Ribulose-1,5-bisphosphate carboxylase of thermophilic hydrogen-oxidizing microorganism Bacillus schlegelii.

Ribulose-1,5-bisphosphate carboxylase was isolated from thermophilic hydrogen-oxidizing Bacillus schlegelii. Molecular mass of the native enzyme is 560,000 and optimal reaction temperature is 70 degrees C. Km value for ribulose 1,5-bisphosphate is 0.27 mM. The carboxylase activity of the enzyme is dependent on Mg2+ with the optimum at 10 mM. The enzyme is an oligomer of L8S8 type with Mr of large subunits and small subunits of 56,000 and 14,000, respectively. Negatively stained enzyme has regular polygonal shape in top view, 12 nm in diameter, with central electron dense patch.