A-dehydrogenases and

A biosensor was designed where a dehydrogenase and an enlarged coenzyme are confined behind an ultrafiltration membrane. The amino acid is determined indirectly, by measuring the fluorescence of the reduced coenzyme (kex 360 nm, kfl 460 nm) produced in reaction 22, with the aid of an optical fiber. The coenzyme is regenerated with pyruvate in a subsequent step, as shown in reaction 23. This biosensor was proposed for determination of L-alanine and L-phenylalanine for monitoring of various metabolic diseases and for dietary management363. 

This enzymic conversion involves two enzymes, a dehydrogenase and an isomerase. The dehydrogenase component oxidizes the hydroxyl group on pregnenolone to a ketone, and requires the oxidizing agent cofactor NAD+ (see Box 11.2). The isomerase then carries out two tautomerism reactions, enolization to a dienol followed by production of the more stable conjugated ketone. 

Hintz SR, Matern D, Strauss A, et al (2002) Early neonatal diagnosis of long-chain 3-hydroxy-acyl coenzyme a dehydrogenase and mitochondrial trifunctional protein deficiencies. Mol Genet Metab 75 120-127... 

The association between a dehydrogenase and NAD or NADP is relatively loose the coenzyme readily diffuses from one enzyme to another, acting as a water-soluble... 

In a fifth method (International Reagents Corp., Kokusai-Kobe, Japan), its first reagent contains the detergent cal-ixarene that converts LDL to a soluble complex. Cholesterol esters of HDL-C and VLDL-C are preferentially hydrolyzed by a cholesterol esterase (chromobacterium), cholesterol oxidase, and hydrazine, which divert the accessible cholesterol to cholestenone hydrazone. A second reagent with deoxycholate brealcs up the LDL-calixarene complex, allowing LDL-C to react with the esterase, a dehydrogenase, and P-NAD to yield cholestenone and fi-NADH, the latter measured by a spectrophotometer. 

The regeneration of rhodopsin following exposure to bright light requires the following steps. The a -trans retinaldehyde combines with phosphotidylethanolamine (PE) to form a protonated Schiff base N-retinylidene-PE. This complex is then exported out of the disk by an ATP-binding cassette (ABC) transporter exclusively located in the retinol disk membrane (ABCR). Outside the disk the a -trans retinaldehyde is reduced to aW-trans retinol hy a dehydrogenase and transported to retinal... 

It is found that the enzyme concerned is a dehydrogenase, and that for oxidation to proceed the coenzyme NAD is required. We have in this oxidation, then, the first example of the dehydrogenase reactions that we discussed in the previous chapter. To add complexity to the picture it was found that the enzyme is multimeric. It contains a suiphydryl group and in fact has three molecules of NAD bound to it - the enzyme also has a requirement for A DP and inorganic phosphate and during the series of reactions ATP is formed directly. This process is called-substrate level phosphorylation to distinguish it from ATP synthesis coupled to the electron transport chain, which is oxidative phosphorylation. 

Naito E, Ozasa H, Ikeda Y, Tanaka K. Molecular cloning and nudeotide sequence of complementary DNAs encoding human short chain acyl-coenzyme A dehydrogenase and the study of the molecular basis of human short chain acyl-coenzyme A dehydrogenase defidency. J Clin Invest. 1989 May 83(5) 1605-13. PubMed dtation... 

Aoyama T, Souri M, Ushikubo S, Kamijo T, Yamaguchi S, Kelley RI, Rhead WJ, Uetake K, Tanaka K, Hashimoto T. Purification of human very-long-chain acyl-coenzyme A dehydrogenase and characterization of its deficiency in seven patients. J Chn Invest. 

Amendt, B.A., and Rhead, W.J., 1986. The multiple acyl-coenzyme A dehydrogenation disorders, glutaric aciduria type II and ethylmalonic-adipic aciduria. Mitochondrial fatty acid oxidation, acyl-coenzyme A dehydrogenase, and electron transfer flavoprotein activities in fibroblasts. Journal of Clinical Investigation. 78 205-213. 

Antozzi C, Garavaglia B, Mora M, Rimoldi M, Morandi L, Ursino E et al. Late-onset riboflavin-responsive myopathy with combined multiple acyl coenzyme A dehydrogenase and respiratory chain deficiency. Neurology 1994 44 2153-2158. 

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