Pyridoxal oxidase

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... 

Pyridoxal oxidase Tryptophan side-chain oxy- Drosophila spp. Pseudomonas spp. 2 (4Fe2S2, 4FAD) Heme... 

Figure 9.1. Interconversion of the vitamin Be vitamers. Pyridoxal kinase, EC 2.7.1.38 pyridoxine oxidase, EC 1.1.1.65 pyridoxamine phosphate oxidase, EC 1.4.3.5 and pyridoxal oxidase, EC 1.1.3.12. Relative molecular masses (Mr) pyridoxine, 168.3 (hydrochloride, 205.6) pyridoxal, 167.2 pyridoxamine, 168.3 (dihydrochloride, 241.1) pyridoxal phosphate, 247.1 pyridoxamine phosphate, 248.2 and 4-pyridoxlc acid, 183.2.

Pyridoxine phosphate may either be used unchanged in enzymic reactions, or it may be split by nonspecific phosphatases to yield pyridoxine and inorganic phosphate. Pyridoxine is then further oxidized to yield 4-pyridoxic acid in the presence of a purified preparation of liver pyridoxic oxidase and aldehyde oxidase. 

Molybdenum functions as the prosthetic group of a small number of enzymes, including xanthine oxidase (which is involved in the metabolism of purines to uric acid for excretion) and pyridoxal oxidase (which metabolizes vitamin to the inactive excretory product pyridoxic acid section 11.9.1). It occurs in an organic complex, molybdopterin, which is chemically similar to folic acid (section 11.11.1) but can be synthesized in the body as long as adequate amounts of molybdenum are available. 

Fig. 2. Biosynthetic pathway for epinephrine, norepinephrine, and dopamine. The enzymes cataly2ing the reaction are (1) tyrosine hydroxylase (TH), tetrahydrobiopterin and O2 are also involved (2) dopa decarboxylase (DDC) with pyridoxal phosphate (3) dopamine-P-oxidase (DBH) with ascorbate, O2 in the adrenal medulla, brain, and peripheral nerves and (4) phenethanolamine A/-methyltransferase (PNMT) with. Cadenosylmethionine in the adrenal...

The deamination of primary amines such as phenylethylamine by Escherichia coli (Cooper et al. 1992) and Klebsiella oxytoca (Flacisalihoglu et al. 1997) is carried out by an oxidase. This contains copper and topaquinone (TPQ), which is produced from tyrosine by dioxygenation. TPQ is reduced to an aminoquinol that in the form of a Cu(l) radical reacts with O2 to form H2O2, Cu(ll), and the imine. The mechanism has been elucidated (Wihnot et al. 1999), and involves formation of a Schiff base followed by hydrolysis in reactions that are formally analogous to those involved in pyridoxal-mediated transamination. 

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.

The synthesis pathway of quinolizidine alkaloids is based on lysine conversion by enzymatic activity to cadaverine in exactly the same way as in the case of piperidine alkaloids. Certainly, in the relatively rich literature which attempts to explain quinolizidine alkaloid synthesis °, there are different experimental variants of this conversion. According to new experimental data, the conversion is achieved by coenzyme PLP (pyridoxal phosphate) activity, when the lysine is CO2 reduced. From cadeverine, via the activity of the diamine oxidase, Schiff base formation and four minor reactions (Aldol-type reaction, hydrolysis of imine to aldehyde/amine, oxidative reaction and again Schiff base formation), the pathway is divided into two directions. The subway synthesizes (—)-lupinine by two reductive steps, and the main synthesis stream goes via the Schiff base formation and coupling to the compound substrate, from which again the synthetic pathway divides to form (+)-lupanine synthesis and (—)-sparteine synthesis. From (—)-sparteine, the route by conversion to (+)-cytisine synthesis is open (Figure 51). Cytisine is an alkaloid with the pyridone nucleus. 

Table 6.2.2 Typical CSF profiles of HVA, 5HIAA and 3-methyldopa (3-MD) for the inborn errors of metabolism associated with a disruption of biogenic amine metabolism. A downward-pointing arrow indicates that a particular metabolite is below the established reference range. An upward pointing arrow is indicative that a metabolite is above the established reference range. WR indicates that the concentration of the metabolite is likely to be within the reference range. AADC Aromatic amino acid decarboxylase, PNPO pyridox(am)ine-5 -phosphate oxidase...

Mills PB, Surtees RAH, Champion MP, Beesley CE, et al (2005) Neonatal epileptic encephalopathy caused by mutations in the PNPO gene encoding pyridox(am)ine 5 -phosphate oxidase. Hum Mol Genet 14 1077-1086... 

Topaquinone (TPQ). Both bacteria and eukaryotes contain amine oxidases that utilize bound copper ions and 02 as electron acceptors and form an aldehyde, NH3, and H202. The presence of an organic cofactor was suggested by the absorption spectra which was variously attributed to pyridoxal phosphate or PQQ. However, isolation from the active site of bovine serum... 

In benzylamine oxidase there is evidence that the amine undergoes transamination with the pyridoxal prosthetic group to give a pyridoxamine, which is then oxidized by dioxygen to give H202 and NH3. The role for the copper is one of activation of the substrate.1346... 

Diamine Oxidases. Diamine oxidases are enzymes that also oxidize amines to aldehydes. The preferred substates are aliphatic diamines in which the chain length is four (putrescine) or five (cadaverine) carbon atoms. Diamines with carbon chains longer than nine will not serve as substrates but can be oxidized by monoamine oxidases. Secondary and tertiary amines are not metabolized. Diamine oxidases are typically soluble pyridoxal phosphate-containing proteins that also contain copper. They have been found in a number of tissues, including liver, intestine, kidney, and placenta. 

Covalent cross-links both between and within the tropocollagen molecules confer strength and rigidity on the collagen fiber. These cross-links are formed between Lys and its aldehyde derivative allysine. Allysine is derived from Lys by the action of the copper-containing lysyl oxidase which requires pyridoxal phosphate for activity. The disease lathyrism is caused by the inhibition of lysyl oxidase by the chemical (3-aminopropionitrile in sweet pea seeds, and results in defective collagen due to the lack of cross-links. 

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