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Abstract:
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Pyridoxal 5'-phosphate (PLP) is the major coenzymatic
form of pyridoxine. There are over one hundred known pyridoxal
5'-phosphate-dependent reactions, most of which are
involved in the metabolism of various amino acids . Pyridoxamine
5'-phosphate can function in aminotransf erase reactions
by the cyclic regeneration of the two active phosphate
forms. Pyridoxal 5'-phosphate-dependent reactions studied
in the nervous system are involved in the catabolism of various
amino acids. The putative neurotransmitters , dopamine,
norepinephrine , serotonin , histamine , aminobutyric acid
and taurine , as well as the sphingoiipids and poly amines are
synthesized by PLP-dependent enzymes. Of these enzymes,
three ( glutamic acid decarboxylase , 5-hydroxytryptophan decarboxylase
and crnithine decarboxylase) seem to have crucial
roles (Fig. '). The clinical effects of pyridoxine deficiency
can be explained on the basis of the known decreases
in the activities of these enzymes |