Noradrenaline,See Norepinephrine

Dihydroxyphenylalanine (for structure see diagram 11) is an amino acid isolated (from the pods and sprouts of Vida fd>a) and first definitely identified in 1913 by Guggenheim (323), who showed it to be identical with synthetic material previously prepared (280). It is widely distributed in certain types of plants (beans, etc.) but is not a normal protein constituent. However, it plays an important part in mammalian metabohsm of tyrosine, as it is the precursor of adrenaline (epinephrine), noradrenaline (arterenol, norepinephrine), and melanin. In this review these substances will be considered only insofar as they account for a portion of normal tyrosine metabolism. 

Catecholamines. The catecholamines, epinephrine (EPl adrenaline) (85), norepinephrine (NE noradrenaline) (86) (see Epinephrine and norepinephrine), and dopamine (DA) (2), are produced from tyrosine by the sequential formation of L-dopa, DA, NE, and finally EPl. EPl and NE produce their physiological effects via CC- and -adrenoceptors, a-Adrenoceptors can be further divided into CC - and a2-subtypes which in turn are divided... 

In addition to their well known role in protein structure, amino acids also act as precursors to a number of other important biological molecules. For example, the synthesis of haem (see also Section 5.3.1), which occurs in, among other tissues, the liver begins with glycine and succinyl-CoA. The amino acid tyrosine which maybe produced in the liver from metabolism of phenylalanine is the precursor of thyroid hormones, melanin, adrenaline (epinephrine), noradrenaline (norepinephrine) and dopamine. The biosynthesis of some of these signalling molecules is described in Section 4.4. 

The adrenal gland and adrenergic neurons continue the synthesis by hydroxylating dopamine into norepinephrine (noradrenaline). Ascorbic acid (vitamin C see p.368) acts as a hydrogen-transferring coenzyme here. 

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