Dopamine 0-mono-oxygenase

Dopamine mono-oxygenase Coproporphyrin decarboxylase Ethylene receptor Methane oxidase Terminal glycine oxidases CP-x type ATP-ase ATx-1 (Lys 7)... 

Why is vitamin C used so extensively as an electron donor There are two main reasons. First, vitamin C is very soluble in water, so it can be concentrated in confined spaces surrounded by membranes (which are made of lipids impermeable to vitamin C). The synthesis of noradrenaline from dopamine, for example, takes place in small membrane-bounded spaces, or vesicles, within cells of the cortex of the adrenal glands. The vitamin C concentration inside these vesicles reaches about 100 times that of blood plasma. As vitamin C is consumed by the enzyme dopamine mono-oxygenase, electrons are passed across the vesicle membrane (via an iron-containing protein, cytochrome b65l), to regenerate vitamin C within the vesicles. Thus, for periods of days or weeks, the intracellular vitamin C needed for physiological tasks can be insulated from changes in plasma levels caused by variations in diet, and maintained at the ideal levels for a particular reaction. 

The formation of the monodehydroascorbate free radical by dopamine P-mono-oxygenase was similarly demonstrated by the acceleration of the reduction of Fe(III)-cytochrome c and by direct spectrophotometry at 360 nm The action of the laccase from the mushroom Agaricus hisporum on catechol yielded also the semiquinone as the result of a one-electron transfer... 

Klinman JP. The copper-enzyme family of dopamine 3-mono-oxygenase and peptidylglycine a-hydroxylating monooxygenase resolving the chemical pathway for substrate hydroxylation. J. Biol. Chem. 2006 281 3013-3016. 

Evans JP, Ahn K, Klinman JP. Evidence that dioxygen and substrate activation are tightly coupled in dopamine fl-mono-oxygenase. Implications for the reactive oxygen species J. Biol. Chem. 2003 278 49691-49698. 

Tyrosine is the precursor for the synthesis of the hormone and neurotransmitter noradrenalin which is formed from dopamine (3,4-dihydroxyphenylethanolamine) by the vitamin C-requiring dopamine j8-mono-oxygenase (also called dopamine-jS-hydroxylase) in the adrenal medulla as shown in Figure 5.14. 

Ascorbic acid is required for many hydroxylase enzymes in the human body. Ascorbic acid is needed for conversion of tyrosine to the neurotransmitter dopamine and further hydroxylation to adrenaline and noradrenaline, for synthesis of carnitine from lysine, and probably for hydroxylation of steroid hormones. Ascorbate is also known to participate in hydroxylation of aromatic drugs and carcinogens via microsomal mono-oxygenase systems of Uver endoplasmic reticulum (31,32). Its role in the formation of collagen is thought to be to maintain iron in its ferrous state for an iron-dependent proline hydroxylase, or to act as a direct source of electrons for reduction of O2 (31). 

E7 Catechol O-methyl transferase (COMT) E8 Guaiacol O-methyl transferase (GOMT) E9 Dopamine p-mono oxygenase ElO Phenylethanolamine N-methyl transferase... 

---