Biogenic amines biosynthetic pathways

Figure 1. Biosynthetic pathways for biogenic amines. In Drosophila and vertebrates decarboxylation of DOPA and 5-hydroxy-tryptophan is catalyzed by the same enzyme, DDC. In vertebrates this enzyme is called amino acid decarboxylase (AADC). Only vertebrates further metabolize dopamine to norepinephrine and epinephrine. TH, tryosine hydroxylase DDC, DOPA decarboxylase DBH, dopamine b-hydroxylase PNMT, phenylethanolamine N-methyltransferase. Tryp-OH tryptophan hydroxylase.

Another strategy of some interest is to deplete biogenic amines such as OA by inhibiting their biosynthesis. Inhibitors of such enzymes in the biosynthetic pathway as aromatic amino acid decarboxylase which converts tyrosine to tyramine, or dopamine 3 -hydroxylase which converts tyramine to OA are known and have interesting effects in insects (e.g. see 52,53)t but a discussion of this area lies outside the scope of this paper. Nevertheless, it is a particularly interesting one since these or related enzymes are also needed to produce catecholamines for cuticular sclerotiza-tion, thus offering dual routes to the discovery of compounds with selectively deleterious actions on insects. 

By analogy with the biogenesis of oximes via oxidation of amino acids or biogenic amines, the biosynthetic pathway for insertion of the ketoxime function into the antibiotic, nocardicin A (18), was shown to be dependent on the oxidation of the corresponding primary amine precursor of 18 by cytochrome PTSO ". Similarly, the formation of the ketoxime bond of verongamine (17) is attributed to the oxidation of a primary amine precursor . 

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