Changing kinetic properties of the two-enzyme phosphoglycerate kinase/NADP-linked glyceraldehyde-3-phosphate dehydrogenase couple from pea chloroplasts during photosynthetic induction |
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| Institution: | 1. College of Chemistry and Chemical Engineering, Central South University, Changsha 410083, PR China;2. Research Institute of Chinese Medicine, Hunan Academy of Chinese Medicine, Changsha 410013, PR China;1. Department of Natural Medicine, Fourth Military Medical University, 710032 Xi’an, China;2. Shaanxi Key Laboratory of Ischemic Cardiovascular Disease, Institute of Basic and Translational Medicine, Xi''an Medical University, 710021 Xi''an, China;1. Institute of Agrophysics, Polish Academy of Sciences, Do?wiadczalna 4, 20-290 Lublin, Poland;2. Department of Plant Anatomy and Cytology, Maria Curie-Sk?odowska University, Akademicka 19, 20-033 Lublin, Poland;1. Department of Biochemistry and Cell Physiology, Voronezh State University, 394006 Voronezh, Russia;2. Department of Biology, Memorial University of Newfoundland, St. John''s, NL A1B 3X9, Canada;1. Institute of Plant Bioenergetics, Faculty of Biology, University of Warsaw, I. Miecznikowa 01, 02-096 Warsaw, Poland;2. Departmentof Biology, Lund University, Sölvegatan 35B, SE-223 62 Lund, Sweden |
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| Abstract: | The kinetics of the two enzyme phosphoglycerate kinase (EC 2.7.2.3)/NADP-linked glyceraldehyde-3-phosphate dehydrogenase (EC 1.2.1.13) couple are negatively cooperative and will also fit a model for two enzymes acting on one substrate. When the chloroplast is illuminated apparent negative cooperativity is reduced; maximal velocity of only one of the two enzymes in the two-enzyme model is increased. Even after light activation the activity of glyceraldehyde-3-phosphate dehydrogenase appears to be too low to support photosynthesis at calculated levels of glycerate-1,3-bisphosphate in isolated chloroplasts (Marques, I.A., Ford, D.M., Muschinek, G. and Anderson, L.E. (1987) Arch. Biochem. Biophys. 252, 458–466). The activity of the coupled reaction is apparently sufficient to support observed rates of CO2 fixation, which suggests that glycerate-1,3-bisphosphate may be channeled from the kinase to the dehydrogenase in vivo. |
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