Ambivalence on the Multiplicity of Mammalian Aromatic L-Amino Acid Decarboxylase
Hydroxytryptophan is decarboxylated to 5-hydroxytryptamine (serotonin) by aromatic L-amino acid decarboxylase which requires pyridoxal phosphate and is widely distributed throughout mammalian tissues, occurring most abundantly in the pineal gland, liver, kidney, adrenal medulla, and striatum. Earlier studies concluded that 3,4-dihydroxyphenylalanine decarboxylase (which catalyzes the decarboxylation of dopa, producing dopamine) and 5-hydroxytryptophan decarboxylase (which catalyzes the decarboxylation of 5-hydroxytryptophan, yielding serotonin) are the same enzyme, which the IUPAC Commission on Biomedical Nomenclature in 1972 named aromatic L-amino acid decarboxylase (EC 22.214.171.124). However, recent studies have questioned the validity of a single enzyme capable of decarboxylating both substrates. For example, since the pineal gland accumulates a large concentration of serotonin, melatonin and other indoleamines, it is assumed that the enzyme functions as a 5-hydroxytryptophan decarboxylase. On the other hand, since the striatum and the adrenal medulla accumulate mainly dopamine, norepinephrine and epinephrine, it is felt that the enzyme primarily decarboxylates dopa. Other factors dealing with the complexity of catalytic process are the results of reports revealing that both dopa decarboxylase and histidine decarboxylase exhibit complete immunochemical cross reactivity, suggesting the presence of similar antigenic recognition sites.
KeywordsPineal Gland Adrenal Medulla Pyridoxal Phosphate Histidine Decarboxylase Dopa Decarboxylase
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- Aures, D., and Hakanson, R., 1971, Histidine decarboxylase, in: “Methods in Enzymology”, Vol. 17, Part B, Colowick, S.P., and Kaplan, N.O., eds., Academic Press, New York, pp. 667–677.Google Scholar
- Blaschko, H., 1939, The specific action of L-dopa decarboxylase, J. Physiol., 96: 50P–51P.Google Scholar
- Blaschko, H., 1945, The amino acid decarboxylase of mammalian tissues, Adv. Enzymol., 5: 67–85.Google Scholar
- Borri Voltattorni, C., Giartosio, A., and Turano, C., 1987, Aromatic L-amino acid decarboxylase from pig kidney, in: “Methods in Enzymology”, Vol. 142, Kaufman, S., ed., Academic Press, New York, pp. 179–187.Google Scholar
- Bowsher, R.R., and Henry, D.P., 1986, Aromatic L-amino acid decarboxylase: biochemistry and functional significance, in: “Neuromethods. 5. Neurotransmitter Enzymes”, Boulton, A.A., Baker, G.B., and Yu, P.H., eds., Humana Press, Clifton, New Jersey, pp. 33–78.Google Scholar
- Dairman, W., and Christenson, J.G., 1972, Dopa decarboxylating activity of human erythrocytes, Fed. Proc, 31: 590.Google Scholar
- Dairman, W., Horst, W.D., Marchell, M.E., and Bautz, G., 1975, The proportionate loss of L-3,4-dihydroxyphenylalanine and L-5-hydroxytryptophan decarboxylating activity in rat central nervous system following intracisternal administration of 5,6-dihydroxytryptamine or 6-hydroxydopamine, J. Neurochem., 24: 619–623.PubMedGoogle Scholar
- Ebadi, M., 1984, Regulation of the synthesis of melatonin and its significance to neuroendocrinology, in: “The Pineal Gland”, Reiter, R.J., ed., Raven Press, New York, pp. 1–37.Google Scholar
- Goldstein, M., Anagnoste, B., Freedman, L.S., Roffman, M., Ebstein, R.P., Park, D.H., Fuxe, K., and Hökfelt, T., 1973, Characterization, localization and regulation of catecholamine synthesizing enzymes, in: “Frontiers in Catecholamine Research”, Usdin, E., and Snyder, S., eds., Pergamon, New York, pp. 69–78.Google Scholar
- Nagatsu, I., Sakai, M., Yoshida, M., and Nagatsu, T., 1988, Aromatic L-amino acid decarboxylase-immunore active neurons in and around the cerebrospinal fluid-contacting neurons of the central canal do not contain dopamine or serotonin in the mouse and rat spinal cord, Brain Res., 475: 91–120.PubMedCrossRefGoogle Scholar
- Sourkes, T.L., 1977, Structure and function of monoamine enzymes, in: “Enzymology of Aromatic Amino Acid Decarboxylase”, Usdin, E., Weiner, N., and Youdim, M.B.H., eds., Marcel Dekker, New York, pp. 477–496.Google Scholar
- Sourkes, T.L., 1987, Aromatic L-amino acid decarboxylase, in: “Methods in Enzymolology”, Vol. 142, Kaufman, S., ed., Academic Press, New York, pp. 170–178.Google Scholar