Alkaloids nucleotide precursor

Purine is the parent heterocyclic compound of the methylxanthines, which are often referred to as the purine alkaloids.1-7 Purine is also the parent compound of some of the base constituents of the nucleotides, which in turn are part of the nucleic acids RNA and DNA. Thus, it appears that the purine alkaloids have similar precursors to nucleic acids. 

Amino acids are not only important for protein synthesis but also serve as precursors for hormones, coenzymes, alkaloids, cell wall polymers, porphyrins, antibiotics, nucleotides, pigments, and neurotransmit-ters. ° A deficiency of one amino acid may result in a negative nitrogen balance (Figure 9). ... 

In addition to their role as the building blocks of proteins, amino acids are precursors of many specialized biomolecules, including hormones, coenzymes, nucleotides, alkaloids, cell wall polymers, porphyrins, antibiotics, pigments, and neurotransmitters. We describe here the pathways to a number of these amino acid derivatives. 

Phase I and II clinical trials indicated that acronycine reduced pain of the spine in some patients with multiple myeloma [280,282,283]. Acronycine has been reported to cause leukopoenia and to have CNS-depressant activity [284], Biochemically, acronycine inhibits incorporation of extracellular nucleosides into the RNA and DNA of leukaemia L-5178Y cell culture. There is, however, no evidence of interaction between acronycine and DNA or inhibition of template activity of DNA. This alkaloid does not inhibit nucleic acid synthesis in the cell, but rather inhibits the accumulation of extracellular uridine or thymidine, as nucleotides, in the intracellular precursor pool [285, 286], Acronycine, acting primarily on membranous organelles [287], seems to interfere with the structure, function and/or turnover of cell membrane components, thereby changing the fluidity of the plasma membrane [288]. 

Besides being fundamental constituents of proteins they are the parent substances from which powerful hormones are derived, for example, adrenaline (epinephrine), noradrenaline (norepinephrine), thyroxine and related substances, 5-hydroxytryptamine (enteramine, serotonin), and the plant hormone indoleacetic acid. Tryptophan is also the precursor of the B vitamin nicotinic acid and hence of part of the important pyridine nucleotides. All three aromatic amino acids are potential precursors of other substances having powerful physiological activity, for example, many of the alkaloids. Errors in the metabolism of the aromatic amino acids in man can give rise to sometimes serious, but fortunately comparatively rare, disorders such as alkaptonuria and phenylketonuria. The numerous metabolic pathways involved in aromatic amino acid metabolism therefore make an important as well as an interesting study. 

The efficient economy of cells is illustrated by the fact that all the different types of proteins and nucleic acids in the living world are synthesized from only 20 amino acids and eight nucleotide bases. These simple molecules are not only used for building structures, but have additional functions as well. For example, amino acids are the precursors for hormones, alkaloids, and porphyrins, and aLso serve as neurotransmitters. Nucleotides are precursors of energy carriers and of coenzymes. These are only a few of the functional compounds synthesized by cells. 

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