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Neurobiology of Pyridoxine a
Author(s) -
DAKSHINAMURTI K.,
PAULOSE C. S.,
VISWANATHAN M.,
SIOW Y. L.,
SHARMA S. K.,
BOLSTER B.
Publication year - 1990
Publication title -
annals of the new york academy of sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.712
H-Index - 248
eISSN - 1749-6632
pISSN - 0077-8923
DOI - 10.1111/j.1749-6632.1990.tb28049.x
Subject(s) - annals , library science , medicine , history , classics , computer science
The diversity of biochemical reactions involving the coenzymatic forms of pyridoxine (vitamin B6) is well recognized. There are over 100 pyridoxal phosphate (PLP) dependent enzymes. Most are involved in catabolic reactions of various amino acids. The crucial role played by pyridoxine in the nervous system is evident from the fact that the putative neurotransmitters, dopamine (DA), norepinephrine (NE), serotonin (5-HT), y-aminobutyric acid (GABA), and taurine as well as the sphingolipids and polyamines are synthesized by PLP-dependent enzymes. Considerable variation exists in the affinities of different apoenzymes for PLP. This explains the observed differential susceptibility of various PLP enzymes to decrease during the progression of pyridoxine deficiency.’ Of the pyridoxine enzymes, three, namely, glutamic acid decarboxylase, 5-hydroxytryptophan decarboxylase, and ornithine decarboxylase, are crucial and can explain most of the neurological defects of pyridoxine deficiency in animals.*~-’ This presentation will focus on the role of pyridoxine in the control of hypothalamo-pituitaryend organ systems, melatonin synthesis, and convulsive seizure activity. The enzyme L-aromatic amino acid decarboxylase (EC 4.1.1.28), which lacks substrate specificity, has been considered to be involved in the formation of the catecholamine as well as ~ero tonin .~ This has been suggested to be a single protein entity, based on immunological evidence of Christenson et al.4 However, the recent demonstration by Ando-Yamamoto et aL4 of immunological cross-reactivity of dihydroxyphenylalanine (DOPA) decarboxylase and histidine decarboxylase using antibodies against these two enzymes suggests the presence of similar antigenic recognition sites inside the native molecules of the decarboxylases that are exposed when the enzymes are denatured. There are many differences in the optimal conditions for enzyme activity, including kinetics, affinity for PLP, activation and inhibition by specific chemicals, and regional differences in the distribution of DOPA and 5hydroxytryptophan (5-HTP) decarboxylases.6-8 During the course of purification of DOPA decarboxylase from bovine striatum, there was a preferential enrichment of