Pyruvate carboxylase model

Figure 10 A hypothetical model of carbon acquisition in the marine diatom Thalassiosira weissflogii. Solid circles represent transporters. Catalyzing enzymes CA, carbonic anhydrase PEPC, phosphoenol pyruvate carboxylase PEPCK phospoenol pyruvate carboxykinase RUBISCO, Ribulose 1-5 bisphosphate Carboxylase Oxygenase (after...

S Daunert, BR Payne, L Bachas. Pyruvate carboxylase as a model for oligosubsti-tuted enzyme-ligand conjugates in homogeneous enzyme immunoassays. Anal Chem 61 2160-2164, 1989. 

Hommes, F.A., Schrijver, J. and Dias, T. (1980), Pyruvate carboxylase deficiency, studies on patients, and on an animal model system. In Inherited Disorders of Carbohydrate Metabolism (eds D. Burman, J.B. Holton and C.A. Pennock), MTP Press Ltd., Lancaster, pp. 269-286. 

Figure 5 Model of phosphorus (P) deficiency-induced physiological changes associated with the release of P-mobilizing root exudates in cluster roots of white lupin. Solid lines indicate stimulation and dotted lines inhibition of biochemical reaction sequences or mclaholic pathways in response to P deliciency. For a detailed description see Sec. 4.1. Abbreviations SS = sucrose synthase FK = fructokinase PGM = phosphoglueomutase PEP = phosphoenol pyruvate PE PC = PEP-carboxylase MDH = malate dehydrogenase ME = malic enzyme CS = citrate synthase PDC = pyruvate decarboxylase ALDH — alcohol dehydrogenase E-4-P = erythrosc-4-phosphate DAMP = dihydraxyaceConephos-phate APase = acid phosphatase.

Mizuhara [65] developed a more adequate model by demonstrating that thiamine catalyzes the decarboxylation of pyruvic acid in basic aqueous solution (pH 8.8). Acetoin is the final product of the reaction. Breslow [66] later showed that the hydrogen in position 2 of the thiazole ring of the coenzyme is exchanged with deuterium when deuterium oxide (D2O) is added to the incubation system. Thus, carbon 2 of the thiamine appears to react in this chemical process. The hydrogen in position 2 is acidic and is thus readily ionized to an anion in basic media (see Fig. 4-7). On the basis of these findings, researchers have proposed the following sequence of reactions to explain the catalytic action of carboxylase. The carbon 2 of the thiazo-... 

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