Pyridoxal dehydrogenases

ALCOHOL DEHYDROGENASE Pyridine nucleotide transhydrogenase, NAD(Pr TRANSHYDROGENASE PYRIDOXAL 4-DEHYDROGENASE PYRIDOXAL KINASE... 

The aerobic degradation of several azaarenes involves reduction of the rings at some stage, and are discussed in Chapter 10, Part 1. Illustrative examples include the degradation of pyridines (3-alkyl-pyridine, pyridoxal) and pyrimidines (catalyzed by dihydropyrimidine dehydrogenases). Reductions are involved in both the aerobic and the anaerobic degradation of uracil and orotic acid. 

Others oxotransferases) (2 pyranopterins bonded to Mo) (8-10 members) Nitrate reduction dissimilatory terminal respiratory oxidase Pyridoxal oxidase Xanthine dehydrogenases Pyrogallol transhydrolase Nitrate to nitrite... 

Figure 2.16. Pathways for the synthesis and metabolism of the catecholamines. A=phenylalanine hydroxylase+pteridine cofactor+Oj B tyrosine hydroxylase+ tetrahydropteridme+Fe+ +Oj C=dopa decarboxylase+pyridoxal phosphate D= dopamine beta-oxidase+ascorbate phosphate+Cu+ +Oj E=phenylethanolamine N-methyltransferase+S-adenosylmethionine l=monoamine oxidase and aldehyde dehydrogenase 2=catechol-0-methyltransferase+S-adenosylmethionine.

PYRIDOXAL 4-DEHYDROGENASE PYRIMIDINE DIMER DNA GLYCOSYLASE Pyroglutamase (ATP-hydrolyzing), 5-OXOPROLINASE... 

Terms in bold are defined in aminotransferases 660 transaminases 660 transamination 660 pyridoxal phosphate (PLP) 660 oxidative deamination 661 l-glutamate dehydrogenase 661 glutamine synthetase 662 glutaminase 663 creatine kinase 664... 

Tissues of the mammalian central nervous system contain a pyridoxal phosphate-dependent glutamate decarboxylase that catalyzes conversion of Glu to y-aminobutyrate (GABA), an inhibitory synaptic transmitter. GABA is degraded by trans-imination with a-oxoglutarate as the acceptor to yield succinic semialdehyde, which then is oxidized to succinate by an NAD-linked dehydrogenase. 

Amino acids NAD(P)H Pyridoxamine 5 -phosphate Pyruvate Amines Pyridoxal 5-phosphate dependent enzymes Dehydrogenases Transaminases Pyridoxal 5-phosphate dependent enzymes Amino acid decarboxylases... 

Chen S-S, Engel PC (1975) The equilibrium position of the reaction of bovine fiver glutamate dehydrogenase with pyridoxal 5 -phosphate. Biochem J 147 351-358... 

E. coli (107, 125). The complexes have recently been reviewed (126). It is possible that lipoamide dehydrogenase also functions in the complexes that oxidatively decarboxylate the a-keto acids resulting from the transamination of valine, isoleucine, and leucine but these have proved difficult to resolve (127). Lipoamide dehydrogenase also functions in the pyridoxal phosphate and tetrahydrofolate-dependent oxidative decarboxylation of glycine in the anaerobic bacterium Peptococcus glyci-nophilus. The reaction in which the protein-bound lipoic acid is reduced is very complex and not yet fully understood the ultimate electron acceptor is NAD+ (112,113,128). 

Pyridoxal phosphate, glyceraldehyde-3-phosphate dehydrogenase and, 22 Pyrogallol, cytochrome c peroxidase and, 353... 

Free pyridoxal either leaves the cells or is oxidized to 4-pyridoxic acid by aldehyde dehydrogenase (which is present in all tissues) and also by hepatic and renal aldehyde oxidases. 4-Pyridoxic acid is actively secreted by the renal tubules, so measurement of the plasma concentration provides an index of renal function (Coburn et al., 2002). There is some evidence that oxidation to 4-pyridoxic acid increases with increasing age in elderly people, the plasma concentration of pyridoxal phosphate is lower, and that of 4-pyridoxic acid higher, than in younger subjects even when there is no evidence of impaired renal function (Bates et al., 1999b). Small amounts of pyridoxal and pyridox-amine are also excreted in the urine, although much of the active vitamin Be that is filtered in the glomerulus is reabsorbed in the kidney tubules. 

Free pyridoxal either leaves the cells or is oxidized to 4-pyridoxic acid by aldehyde dehydrogenase (which is present in all tissues) and also by hepatic and renal aldehyde oxideises. 4-Pyridoxic acid is actively secreted by the renal tubules, so meeisurement of the pleisma concentration provides an index of rened function (Coburn et ed., 2002). There is some evidence that oxidation to... 

Pyridoxal 5 -phosphate is an essential cofactor for many enzymes responsible for the metabolic conversions of amino acids. The fourth step in its synthetic pathway in Escherichia coli is catalyzed by the divalent metal ion-dependent enzyme 4-hydroxythreonine-4-phosphate dehydrogenase (PdxA), which converts 4-hydroxy-l-threonine phosphate (HTP) to 3-amino-2-oxopropyl phosphate. The... 

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