C nuclear magnetic resonance study of the CO(2) activation of ribulosebisphosphate carboxylase from Rhodospirillum rubrum.

Ribulosebisphosphate carboxylase [3-phospho-D-glycerate carboxy-lyase (dimerizing), EC 4.1.1.39] from Rhodospirillum rubrum is activated by CO(2) and Mg(2+). (13)C NMR spectra were determined for the unactivated enzyme and for enzyme that had been activated by (13)CO(2) and Mg(2+). In addition to the expected resonance for H(13)CO(3) (-)/CO(3) (2-) at 161.8 ppm downfield from tetramethylsilane, the spectrum of the activated enzyme shows a broad resonance at 164.9 ppm. Analogy with previous NMR studies of (13)CO(2) binding to hemoglobin [Morrow, J. S., Keim, P., Visscher, R. B., Marshall, R. C. & Gurd, F. R. N. (1973) Proc. Natl. Acad. Sci. USA 70, 1414-1418], to myoglobin, and to amino acids [Morrow, J. S., Keim, P. & Gurd, F. R. N. (1974) J. Biol. Chem. 249, 7484-7494] suggests that the CO(2) activation of ribulosebisphosphate carboxylase involves formation of a carbamate between an enzyme amino group and CO(2).