Photosynthetic and Photorespiratory Enzymes in Widely Divergent Plant Species with Special Reference to the MossCeratodon purpureus: Properties of Ribulose Bisphosphate Carboxylase/ Oxygenase, Phosphoenolpyruvate Carboxylase and Glycolate Oxidase

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Abstract
Rintamäki, E. and Aro, E.-M. 1985. Photosynthetic and photorespiratory enzymes in widely divergent plant species with special reference to the moss Ceratodon purpureus: Properties of ribulose bisphosphate carboxylase/oxygenase, phosphoenolpyruvate carboxylase and glycolate oxidase.—J. exp. Bot. 36: 1677–1684. Km(CO2) values and maximal velocities of ribulose bisphosphate carboxylase/oxygenase (E.C. 4.1.1.39) were determined for six plant species growing in the wild, consisting of a moss, a fern and four angiosperms. The maximum velocities of the RuBP carboxylases varied from 0.13 to 0.;62 μmol CO2 fixed min−1 mg−1 soluble protein and the Km(CO2) values from 15 to 22 mmol m−3 CO2. The highest Km(CO2) values found were for the moss, Ceratodon purpureus, and the grass, Deschampsia flexuosa. These plants also had the highest ratios of the activities of RuBP carboxylase to RuBP oxygenase. Glycolate oxidase (E.C. 1.1.3.1) activities were slightly lower in D.flexuosa, but not in C. purpureus, than for typical C3 species. Phosphoenolpyruvate carboxylase (E.C. 4.1.1.31) was not involved in the photosynthetic carboxylation by these two plants. However, another grass, Phragmites australis, was intermediate in PEP carboxylase activity between C3 and C4 plants The properties of RuBP carboxylase/oxygenase are discussed in relation to the activities of PEP carboxylase and glycolate oxidase and to the internal CO2 concentration.