Dehydrogenase malate

AMI was used for the QM system with link atoms for QM/MM partitioning, and CHARMM22 parameters [20] for the MM atoms. The van der Waals parameters of the QM atoms which were used had been developed by fitting QM/MM interaction energies (for representative small molecules with a TIP3P water molecule) to RHF/6-31G( i) results for the same systems [126,162]. 

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Enzymes, measured in clinical laboratories, for which kits are available include y-glutamyl transferase (GGT), alanine transferase [9000-86-6] (ALT), aldolase, a-amylase [9000-90-2] aspartate aminotransferase [9000-97-9], creatine kinase and its isoenzymes, galactose-l-phosphate uridyl transferase, Hpase, malate dehydrogenase [9001 -64-3], 5 -nucleotidase, phosphohexose isomerase, and pymvate kinase [9001-59-6]. One example is the measurement of aspartate aminotransferase, where the reaction is followed by monitoring the loss of NADH ... 

A free energy study of malate dehydrogenase [29] using semiempirical QM-MM methods has also been reported, and that shidy also attributes many of the benefits to simulation of enzyme reactions found in the BPTP shidy. 

G Wu, A Eiser, B ter Kuile, A Sail, M Muller. Convergent evolution of Trichomonas vaginalis lactate dehydrogenase from malate dehydrogenase. Proc Natl Acad Sci USA 96 6285-6290, 1999. 

NAD (P) " -dependent enzymes are stereospecific. Malate dehydrogenase, for example, transfers a hydride to die pro-/ position of NADH, whereas glyceraldehyde-3-phosphate dehydrogenase transfers a hydride to die pro-5 position of the nicotinamide. Alcohol dehydrogenase removes a hydride from the pro-i position of edianol and transfers it to die pro-i position of NADH. 

A typical intramitochondrial concentration of malate is 0.22 mM. If the [NAD ]/[NADH] ratio in mitochondria is 20 and if the malate dehydrogenase reaction is at equilibrium, calculate the intramitochondrial concentration of oxaloacetate at 25°C. 

FIGURE 20,20 (a) The structure of malate dehydrogenase, (b) The active site of malate dehydrogenase. Malate is shown in red NAD" is blue. 

Glyoxysomes do not contain all the enzymes needed to run the glyoxylate cycle succinate dehydrogenase, fumarase, and malate dehydrogenase are absent. Consequently, glyoxysomes must cooperate with mitochondria to run their cycle (Figure 20.31). Succinate travels from the glyoxysomes to the mitochondria, where it is converted to oxaloacetate. Transamination to aspartate follows... 

The second electron shuttle system, called the malate-aspartate shuttle, is shown in Figure 21.34. Oxaloacetate is reduced in the cytosol, acquiring the electrons of NADH (which is oxidized to NAD ). Malate is transported across the inner membrane, where it is reoxidized by malate dehydrogenase, converting NAD to NADH in the matrix. This mitochondrial NADH readily enters the electron transport chain. The oxaloacetate produced in this reaction cannot cross the inner membrane and must be transaminated to form aspartate, which can be transported across the membrane to the cytosolic side. Transamination in the cytosol recycles aspartate back to oxaloacetate. In contrast to the glycerol phosphate shuttle, the malate-aspartate cycle is reversible, and it operates as shown in Figure 21.34 only if the NADH/NAD ratio in the cytosol is higher than the ratio in the matrix. Because this shuttle produces NADH in the matrix, the full 2.5 ATPs per NADH are recovered. 

Compartmentation of these reactions to prevent photorespiration involves the interaction of two cell types, mescrphyll cells and bundle sheath cells. The meso-phyll cells take up COg at the leaf surface, where Og is abundant, and use it to carboxylate phosphoenolpyruvate to yield OAA in a reaction catalyzed by PEP carboxylase (Figure 22.30). This four-carbon dicarboxylic acid is then either reduced to malate by an NADPH-specific malate dehydrogenase or transaminated to give aspartate in the mesophyll cells. The 4-C COg carrier (malate or aspartate) then is transported to the bundle sheath cells, where it is decarboxylated to yield COg and a 3-C product. The COg is then fixed into organic carbon by the Calvin cycle localized within the bundle sheath cells, and the 3-C product is returned to the mesophyll cells, where it is reconverted to PEP in preparation to accept another COg (Figure 22.30). Plants that use the C-4 pathway are termed C4 plants, in contrast to those plants with the conventional pathway of COg uptake (C3 plants). 

NADPH can be produced in the pentose phosphate pathway as well as by malic enzyme (Figure 25.1). Reducing equivalents (electrons) derived from glycolysis in the form of NADH can be transformed into NADPH by the combined action of malate dehydrogenase and malic enzyme ... 

A less time consuming alternative to the saponifica-tion/malate dehydrogenase assay is the albeit less specific measurement of the carboxylic ester groups according to Kak c and Vejdelek [10]. The sample (160 /xl) is... 

The final step is the oxidation of (S)-malate by NAD+ to give oxaloacetate, a reaction catalyzed by malate dehydrogenase. The citric acid cycle has now returned to its starting point, ready to revolve again. The overall result of the cycle is... 

Enzymes a) citrate synthase b) aconitase c) isocitrate dehydrogenase d) a-oxoglutarate dehydrogenase e) succiny CoA synthetase f) succinate dehydrogenase g) fumarase h) malate dehydrogenase i) nucleoside diphosphokinase. 

Malate dehydrogenase Respiratory chain oxidation of 2 NADH 6 Net 30... 

In pigeon, chicken, and rabbit liver, phospho-enolpymvate carboxykinase is a mitochondrial enzyme, and phosphoenolpyruvate is transported into the cytosol for gluconeogenesis. In the rat and the mouse, the enzyme is cytosolic. Oxaloacetate does not cross the mitochondrial inner membrane it is converted to malate, which is transported into the cytosol, and convetted back to oxaloacetate by cytosolic malate dehydrogenase. In humans, the guinea pig, and the cow, the enzyme is equally disttibuted between mitochondria and cytosol. 

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.

Mitochondrial L-malate dehydrogenase (bovine heart muscle)1501... 

Bonnete, F. Madern, D. Zaccai, G., Stability against denaturation mechanisms in halophilic malate dehydrogenase adapt to solvent connditions, 7. Mol. Biol. 1994, 244, 436-447... 

The work in the biosensor industry permitted the testing and proved of stability and reproducibility of enzymes, within the conditions employed in that area. Enzymes with demonstrated stability include lactate oxidase, malate dehydrogenase, alcohol oxidase, and glutamate oxidase. 

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