Furthermore, considering both the nature and the complexity of the chemical reaction, its kinetic properties are unremarkable. Although not unique to Rubisco, oxygenation is not systematically observed in enolate and enamine forming enzymes and cannot be considered as an inevitable consequence of the mechanism.
It is more likely the result of a compromise between chemical and metabolic imperatives. This makes rubisco the most plentiful single enzyme on the Earth. Rubisco also shows an embarrassing lack of specificity. Unfortunately, oxygen molecules and carbon dioxide molecules are similar in shape and chemical properties. In proteins that bind oxygen, like myoglobin, carbon dioxide is easily excluded because carbon dioxide is slightly larger. But in rubisco, an oxygen molecule can bind comfortably in the site designed to bind to carbon dioxide.
Rubisco then attaches the oxygen to the sugar chain, forming a faulty oxygenated product. The plant cell must then perform a costly series of salvage reactions to correct the mistake. Rubisco from spinach left and photosynthetic bacteria right. Plants and algae build a large, complex form of rubisco shown on the left , composed of eight copies of a large protein chain shown in orange and yellow and eight copies of a smaller chain shown in blue and purple.
The protein shown here is taken from spinach leaves coordinates may be found in the PDB entry 1rcx ; the tobacco enzyme may be found in 1rlc. Many enzymes form similar symmetrical complexes. Often, the interactions between the different chains are used to regulate the activity of the enzyme in the process known as allostery.
Rubisco, however, seems to be rigid as a rock, with each of the active sites acting independently of one another. PubMed Abstract Google Scholar. The diversity and coevolution of Rubisco, plastids, pyrenoids, and chloroplast-based CO 2 -concentrating mechanisms in algae. J, Bot. Bainbridge, G.
Engineering Rubisco to change its catalytic properties. Bar-Even, A. The moderately efficient enzyme: futile encounters and enzyme floppiness. Biochemistry 54, — The moderately efficient enzyme: evolutionary and physicochemical trends shaping enzyme parameters.
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Pangloss right? Hanson, D. Breaking the rules of Rubisco catalysis. Igamberdiev, A. Control of Rubisco function via homeostatic equilibration of CO 2 supply. Plant Sci. Jordan, D. Kannappan, B. Redefinition of Rubisco carboxylase reaction reveals origin of water for hydration and new roles for active-site residues. Koralov, L. Theory of Probability and Random Processes. Berlin; Heidelberg: Springer-Verlag. Google Scholar. Kubien, D. The biochemistry of Rubisco in Flaveria.
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Parry, M. Rubisco activity and regulation as targets for crop improvement. Peterhansel, C. Private Access. Remember Me. Lost Password? Homepage Contact Public Documents.
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