Amino dehydrogenases

D-glyceric acid + NH amino acid(s) + selenol(s) glycerate dehydrogenase + Ala dehydrogenase 202... 

ADH Horse liver alcohol dehydrogenase, an enzyme dimer of identical 374 amino acid polypeptide chains. The amino acid composition of ADH is reasonably representative of die norm for water-solnble proteins. 

The NAD- and NADP-dependent dehydrogenases catalyze at least six different types of reactions simple hydride transfer, deamination of an amino acid to form an a-keto acid, oxidation of /3-hydroxy acids followed by decarboxylation of the /3-keto acid intermediate, oxidation of aldehydes, reduction of isolated double bonds, and the oxidation of carbon-nitrogen bonds (as with dihydrofolate reductase). 

The unripened fruit of the akee tree contains hypoglycin, a rare amino acid (Figure 24.14). Metabolism of hypoglycin yields methylenecydopropylacetyl-CoA (MCPA-CoA). Acyl-CoA dehydrogenase will accept MCPA-CoA as a substrate,... 

The acetyl-CoA derived from amino acid degradation is normally insufficient for fatty acid biosynthesis, and the acetyl-CoA produced by pyruvate dehydrogenase and by fatty acid oxidation cannot cross the mitochondrial membrane to participate directly in fatty acid synthesis. Instead, acetyl-CoA is linked with oxaloacetate to form citrate, which is transported from the mitochondrial matrix to the cytosol (Figure 25.1). Here it can be converted back into acetyl-CoA and oxaloacetate by ATP-citrate lyase. In this manner, mitochondrial acetyl-CoA becomes the substrate for cytosolic fatty acid synthesis. (Oxaloacetate returns to the mitochondria in the form of either pyruvate or malate, which is then reconverted to acetyl-CoA and oxaloacetate, respectively.)... 

Alcohol dehydrogenase, 178 Alkaline error, 149 Alkaline phosphatase, 185 Alkanethiols, 46, 123 Alkoxide precursor, 120 Amino acids, 92, 187 Ammonium sensor, 181, 182 Amperometric sensors, 172 Aniline, 35, 39... 

Inherited defects in the enzymes of (3-oxidation and ketogenesis also lead to nonketotic hypoglycemia, coma, and fatty hver. Defects are known in long- and short-chain 3-hydroxyacyl-CoA dehydrogenase (deficiency of the long-chain enzyme may be a cause of acute fetty liver of pr nancy). 3-Ketoacyl-CoA thiolase and HMG-CoA lyase deficiency also affect the degradation of leucine, a ketogenic amino acid (Chapter 30). 

The enzymes glutamate dehydrogenase, glutamine synthetase, and aminotransferases occupy central positions in amino acid biosynthesis. The combined effect of... 

Transamination channels a-amino acid nitrogen into glutamate. L-Glutamate dehydrogenase (GDH) occupies a central position in nitrogen metabolism. 

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