The CO(2)/O(2) specificity factor of sucrose gradient purified ribulose 1,5-bisphosphate carboxylase/oxygenase from the C(3)-C(4) intermediate plants Moricandia arvensis (79 +/- 1) and Panicum milioides (89 +/- 2) was similar to the respective values of the enzyme from the closely related C(3)