Characterization of the oxygenase activity in a mutant of Chlamydomonas reinhardi exhibiting altered ribulosebisphosphate carboxylase

The effects of bivalent cations on ribulose bisphosphate carboxylase/oxygenase

The half-saturation constants for binding of the bivalent cations (Mg2+, Ni2+, Co2+, Fe2+ and Mn2+) to ribulose bisphosphate carboxylase/oxygenase from Glycine max and Rhodospirillum rubrum were measured. The values obtained were dependent on the enzyme and the cation present, but were the same for both oxygenase and carboxylase activities. Ribulose bisphosphate rather than its cation complex was the true substrate. The kinetic parameters Vmax.(CO2), Vmax.(O2), Km(CO2), Km(O2), and K1(O2) were determined for both enzymes and each cation activator. The evolutionary and mechanistic implications of these data are discussed.

Mutations altering the catalytic activity of a plant-type ribulose biphosphate carboxylase/oxygenase in Alcaligenes eutrophus

Use of a bacterial system has allowed the isolation of several mutationally altered species of ribulose-1,5-bisphosphate carboxylase/oxygenase having a wide range of catalytic activities. Biochemical and serological techniques were used to classify the mutant strains into three groups: (1) no detectable ribulose-1,5-bisphosphate carboxylase/oxygenase protein present (both subunits missing); (2) mutant strains having ribulose-1,5-bisphosphate carboxylase/oxygenases with lowered specific activities; and (3) mutant strains producing large quantities of catalytically inactive ribulose-1,5-bisphosphate carboxylase/oxygenase.