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. Author manuscript; available in PMC: 2019 Jan 4.
Published in final edited form as: Parkinsonism Relat Disord. 2016 Dec 15;35:88–91. doi: 10.1016/j.parkreldis.2016.12.011

Fig. 1. Concept diagram about sources and metabolic fate of dopamine in putamen tissue.

Fig. 1.

Tyrosine hydroxylase (TH) catalyzes the conversion of tyrosine to DOPA, and L-aromatic-amino-acid decarboxylase (LAAAD) converts DOPA to dopamine (DA). Most of the DA in putamen tissue is in vesicles, due to uptake mediated by the vesicular monoamine transporter (VMAT). Cytoplasmic DA can be metabolized by monoamine oxidase (MAO) in the outer mitochondrial membrane to form 3,4-dihydroxyphenylacetaldehyde (DOPAL), which is metabolize by aldehyde dehydrogenase (ALDH) to form 3,4-dihydroxyphenylacetic acid (DOPAC) or by aldehyde/aldose reductase (AR) to form 3,4-dihydroxyphenylethanol (DOPET). Cytoplasmic DA can oxidize spontaneously to form DA-quinone (DA-Q) and then 5-S-cysteinyl-DA (Cys-DA), and cytoplasmic DOPA can oxidize spontaneously to form DOPA-quinone (DOPA-Q) and then 5-S-cysteinyl-DOPA (Cys-DOPA). The rectangle in aqua corresponds to products of TH proximal to DA; in pink to cytoplasmic DA metabolites; and in green to vesicular DA.