title: Distribution of fallover in the carboxylase reaction and fallover-inducible sites among ribulose 1,5-bisphosphate carboxylase/oxygenases of photosynthetic organisms.
abstract: The biphasic reaction course, fallover, of carboxylation catalysed by ribulose 1,5-bisphosphate carboxylase/oxygenase (RuBisCO) has been known as a characteristic of the enzyme from higher land plants. Fallover consists of hysteresis in the reaction seen during the initial several minutes and a very slow suicide inhibition by inhibitors formed from the substrate ribulose-1,5-bisphosphate (RuBP). This study examined the relationship between occurrence of fallover and non-catalytic RuBP-binding sites, and the putative hysteresis-inducible sites (Lys-21 and Lys-305 of the large subunit in spinach RuBisCO) amongst RuBisCOs of a wide variety of photosynthetic organisms. Fallover could be detected by following the course of the carboxylase reaction at 1 mM RuBP and the non-catalytic binding sites by alleviation of fallover at 5 mM RuBP. RuBisCO from Euglena gracilis showed the same linear reaction course at both RuBP concentrations, indicating an association between an absence of fallover and an absence of the non-catalytic binding sites. This was supported by the results of an equilibrium binding assay for this enzyme with a transition state analogue. Green macroalgae and non-green algae contained the plant-type, fallover enzyme. RuBisCOs from Conjugatae, Closterium ehrenbergii, Gonatozygon monotaenium and Netrium digitus, showed a much smaller decrease in activity at 1 mM RuBP than the spinach enzyme and the reaction courses of these enzymes at 5 mM RuBP were almost linear. RuBisCO of a primitive type Conjugatae, Mesotaenium caldariorum, showed the same linear course at both RuBP concentrations. Sequencing of rbcL of these organisms indicated that Lys-305 was changed into arginine with Lys-21 conserved.
authors.affiliation: Plant Molecular Physiology Laboratory, Research Institute of Innovative Technology for the Earth (RITE), Kyoto, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Uemura
authors.forename: H
authors.initials: H
authors.lastname: Tokai
authors.forename: T
authors.initials: T
authors.lastname: Higuchi
authors.forename: H
authors.initials: H
authors.lastname: Murayama
authors.forename: H
authors.initials: H
authors.lastname: Yamamoto
authors.forename: Y
authors.initials: Y
authors.lastname: Enomoto
authors.forename: S
authors.initials: S
authors.lastname: Fujiwara
authors.forename: J
authors.initials: J
authors.lastname: Hamada
authors.forename: A
authors.initials: A
authors.lastname: Yokota
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001419:Bacteria / Q000145:classification; D002384:Catalysis; D002478:Cells, Cultured; D004790:Enzyme Induction; D005056:Euglena gracilis / Q000201:enzymology; D056890:Eukaryota / Q000145:classification / Q000201:enzymology; D007700:Kinetics; D010802:Phylogeny; D010944:Plants / Q000145:classification / Q000201:enzymology*; D012273:Ribulose-Bisphosphate Carboxylase / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D018724:Spinacia oleracea / Q000201:enzymology
chemical_list: D012273:Ribulose-Bisphosphate Carboxylase