The Km(CO2) ancl Vmax of ribulose 1,5-bisphosphate (RuBP) carboxylase and its protein ratio to total soluble protein from Oryza species including cultivars (25 varieties) and wild types (11 species, 21 strains) were surveyed. Their variabilities among cultivars of O. sativa were very small. The averages of the Km(CO2) and Vmax values and the ratio of carboxylase to soluble protein, and their standard errors were 10.2±1.0μM, 1.72±0.13units.mg−1 (pH 8.0 and 25°C) and 52±2%, respectively. However, some differences seemed to exist based on genome constitution in the Oryza genus. RuBP carboxylases from the species with the AgAg genome, O. graberrima and O. breviligulate, exhibited low Km(CO2) values (8.0±0.8 μM). High Vmax was associated with the CC genome, O. eichingeri and O. officinalis (2.08±0.15 units.mg−1). A higher ratio of RuBP carboxylase protein to soluble protein was found for the AA genome, O. sativa and O. perennis.
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Makino et al. (1987) studied this question.