Activation and regulation of ribulose bisphosphate carboxylase-oxygenase in the absence of small subunits

• Published in: The Journal of biological chemistry Vol. 254; no. 20; pp. 10184 - 10189
• Main Authors: Whitman, W B, Martin, M N, Tabita, F R
• Format: Journal Article
• Language: English
• Published: United States American Society for Biochemistry and Molecular Biology 25-10-1979
• Subjects: Bicarbonates - pharmacology; Carboxy-Lyases - metabolism; Enzyme Activation; Kinetics; Magnesium - pharmacology; Pyridoxal Phosphate - pharmacology; Rhodospirillum rubrum - enzymology; Ribulose-Bisphosphate Carboxylase - metabolism
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(19)86691-7

Ribulose 1,5-bisphosphate carboxylase from Rhodospirillum rubrum requires CO2 and Mg2+ for activation of both CO2, both the
carboxylase and oxygenase activities are stimulated by 6-phoshpo-D-gluconate, fructose 1,6-bisphosphate, 2-phosphoglycolate,
3-phosphoglycerate, NADPH, and fructose 6-phosphate. The carboxylase activity is not activated by ribose 5-phosphate. The
substrate, ribulose bisphosphate, neither activates nor inhibits the CO2 and Mg2+ activation of this enzyme. Activation by
CO2 and Mg2+ is rapid and results in increased susceptibility to active-site-directed protein modification reagents. Because
the R. rubrum carboxylase-oxygenase is a dimer of large subunits and contains no small subunits, these results suggest that
the effector binding sites of the higher plant enzyme may also be found on the large subunit.