Bioinformatics Research Laboratory, IBI Biosolutions Pvt. Ltd. India

Dopamine synthesis

Dopamine is a catecholamine neurotransmitter found predominately in the central nervous system. It is synthesized from the amino acid tyrosine, which is converted to L-dihydroxyphenylalanine (L-DOPA) by the enzyme tyrosine hydroxylase. Dihydroxyphenylalanine is converted to dopamine by the enzyme DOPA decarboxylase (or aromatic amino acid decarboxylase) which is found in the cytoplasm.

Dopamine is found in three major pathways in the central nervous system. A dopamine projection from the hypothalamus plays an important role in the regulation of prolactin release from the pituitary gland. Dopamine also is synthesized by neurons in the ventral tegmental area, which projects to the prefrontal cortex and the basal forebrain, including the nucleus accumbens. Another important dopamine pathway is from the substantia nigra pars compacta to the neostriatum.

Dopamine can be further metabolized to norepinephrine by the enzyme dopamine-hydroxylase, in neurons containing the enzyme. Catecholamines can be taken back up into neurons after release via the dopamine transporter, or metabolized by monoamine oxidase (to 3,4,-dihydroxyphenylacetic acid) or catechol-O-methyltransferase (to 3-methoxytyramine). These enzymes are major mechanisms for inactivation of catecholamines (and monoamines). Action by both enzymes results in the formation of homovanillic acid (3-methoxy-4hydroxy-phenylacetic acid).

Dopamine Synthesis Flow Chart

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