Dehydrogenases glycerol dehydrogenase

Novel glycerol and formaldehyde selective sensors based on pEI-Sensitive Field Effect Transistors as transducers and Glycerol Dehydrogenase and Formaldehyde Dehydrogenase as biorecognition elements have been developed. The main analytical parameters of the sensors have been investigated and will be discussed. 

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. 

Step 3 of Figure 29.3 Alcohol Oxidation The /3-hydroxyacyl CoA from step 2 is oxidized to a /3-ketoacyl CoA in a reaction catalyzed by one of a family of L-3-hydroxyacyl-CoA dehydrogenases, which differ in substrate specificity according to the chain length of the acyl group. As in the oxidation of sn-glycerol 3-phosphate to dihydroxyacetone phosphate mentioned at the end of Section 29.2, this alcohol oxidation requires NAD+ as a coenzyme and yields reduced NADH/H+ as by-product. Deprotonation of the hydroxyl group is carried out by a histidine residue at the active site. 

Another pathway is the L-glycerol 3-phosphate shuttle (Figure 11). Cytosolic dihydroxyacetone phosphate is reduced by NADFl to s.n-glycerol 3-phosphate, catalyzed by s,n-glycerol 3-phosphate dehydrogenase, and this is then oxidized by s,n-glycerol 3-phosphate ubiquinone oxidoreductase to dihydroxyacetone phosphate, which is a flavoprotein on the outer surface of the inner membrane. By this route electrons enter the respiratory chain.from cytosolic NADH at the level of complex III. Less well defined is the possibility that cytosolic NADH is oxidized by cytochrome bs reductase in the outer mitochondrial membrane and that electrons are transferred via cytochrome b5 in the endoplasmic reticulum to the respiratory chain at the level of cytochrome c (Fischer et al., 1985). 

Insulin stimulates lipogenesis by several other mechanisms as well as by increasing acetyl-CoA carboxylase activity. It increases the transport of glucose into the cell (eg, in adipose tissue), increasing the availability of both pyruvate for fatty acid synthesis and glycerol 3-phosphate for esterification of the newly formed fatty acids, and also converts the inactive form of pyruvate dehydrogenase to the active form in adipose tissue but not in liver. Insulin also—by its ability to depress the level of intracellular cAMP—inhibits lipolysis in adipose tissue and thereby reduces the concentration of... 

Liyanage H, S Kashket, M Young, ER Kashket (2001) Clostridium beijerinckii and Clostridium difficile detoxify methylglyoxal by a novel mechanism involving glycerol dehydrogenase. Appl Environ Microbiol 67 2004-2010. 

Minteer and co-workers have also exploited the broad substrate specificity of PQQ-dependent alcohol dehydrogenase and aldehyde dehydrogenase from Gluconobacter species trapped within Nahon to oxidize either ethanol or glycerol at a fuel cell anode [Arechederra et al., 2007]. Although the alcohol dehydrogenase incorporates a series of heme electron transfer centers, it is unlikely that many enzyme molecules trapped within the mediator-free Nahon polymer are electronically engaged at the electrode. 

GLYCEROL PHOSPHATE DEHYDROGENASE IS AN NADH OXIDIZING ENZYME RELATED TO GLYCOLYSIS 541... 

Glycerol phosphate dehydrogenase (GPDH) is indirectly associated with glycolysis and reduces dihydroxyacetone phosphate to glycerol-3-phosphate, oxidizing NADH... 

DBM dopamine P-monooxygenase GDPH glycerol phosphate dehydrogenase... 

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