Biosynthesis, channeled

Multienzymatic Proteins in Mammalian Pyrimidine Biosynthesis Channeling of Intermediates to Avoid Futile Cycles Richard I. Christopherson, Thomas W. Traut, and Mary Ellen Jones... 

Natural product synthesis poses the challenge to consider and develop new pathways of structural transformation. Natural products as targets for synthetic research possess a special fertility in this regard, because the structural channels of biosynthesis are not necessarily the conduits of organic synthesis. A. Eschenmoser19... 

Five of the first six enzyme activities of pyrimidine biosynthesis reside on multifunctional polypeptides. One such polypeptide catalyzes the first three reactions of Figure 34-2 and ensures efficient channeling of carbamoyl phosphate to pyrimidine biosynthesis. A second bifunctional enzyme catalyzes reactions 5 and 6. 

As with the biosynthesis of anandamide, the biosynthesis of 2-AG is also triggered by increases of intracellular calcium ions that result from neuronal activity. High frequency stimulation of neurons produced a fourfold increase of 2-AG accumulation compared with controls, and this was prevented by sodium ion channel blocking or removal of calcium ions (Stella, 1997). The concentration of 2-AG in depolarized neurons reached 1 to 2 pM, significantly higher than anandamide and sufficient to substantially activate CB1 (Stella, 1997). 

Since only less than 10% of G-6-P is channeled into the pentose phosphate cycle (under physiological conditions this percentage varies depending on the different tissues), the question must be discussed, what is the importance of this shunt. With regard to the resulting compounds Eqs. [(3), (5), (6), (7)] one mole NADPH2 appears twice. Furthermore, pentose phosphates are furnished for biosynthesis of nucleotides, nucleic acids, and fatty acids (D5, D6, DIO, H13, M5). 

Segal DS, Callaghan M, MandeU AJ Alterations in behaviour and catecholamine biosynthesis induced by lithium. Nature 254 58-59, 1975 Seguela P, Wadiche J, Dineley-Miller K, et al Molecular cloning, functional properties, and distribution of rat brain dJ a nicotinic cation channel highly permeable to calcium. J Neurosci 13 596-604, 1993... 

Geosmin synthesis in channel catfish aquaculture systems, 322-333 biosynthesis, 328-329 occurrence in organisms, 324,325r odor quality, 13 synthesis, 322,323/ synthetic mutant selection, 330-333 Glucosyloxyethyl methacrylate polymerization, 224,225/ synthesis and toxicity, 222,224 Glucosyloxyethyl methacrylate polymers potential applications, 226r properties, 224-227... 

Jorgensen K, Rasmussen AV, Morant M, Nielsen AH, Bjarnholt N, Zagrobelny M, Bak S, Moller BL. (2005). Metabolon formation and the metabolic channelling in the biosynthesis of NPs. Current Opinion in Plant Science, 8,280-291. 

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