Isoprene biosynthetic process

Evaluation of Isoprene Biosynthetic Process from Different Substrates... 

Coenzyme Q is well defined as a crucial component of the oxidative phosphoiylation system in the mitochondria, where energy derived from the products of fatty acids and carbohydrates is converted into ATP to drive cellular machinery and biosynthetic processes (Figure 36.3). Coenzyme Q (also known as ubiquinone) was discovered by Fred Crane and his colleagues in 1957 in beef heart mitochondria. Karl Folkers and his associates elucidated its chemical structure in 1958. Coenzyme Q is composed of a homologous series of compounds differing in the length of the isoprene side chain, and coenzyme Qio, the homologue present in humans and several other species, has 10... 

Steroids are members of a large class of lipid compounds called terpenes. Using acetate as a starting material, a variety of organisms produce terpenes by essentially the same biosynthetic scheme (Fig. 8). The self-condensation of two molecules of acetyl coenzyme A (CoA) forms acetoacetyl CoA. Condensation of acetoacetyl CoA with a third molecule of acetyl CoA, then followed by an NADPH-mediated reduction of the thioester moiety produces mevalonic acid [150-97-0] (72). Phosphorylation of (72) followed by concomitant decarboxylation and dehydration processes produce isopentenyl pyrophosphate. Isopentenyl pyrophosphate isomerase establishes an equilibrium between isopentenyl pyrophosphate and 3,3-dimethylallyl pyrophosphate (73). The head-to-tail addition of these isoprene units forms geranyl pyrophosphate. The addition of another isopentenyl pyrophosphate unit results in the sesquiterpene (C15) famesyl pyrophosphate (74). Both of these head-to-tail additions are catalyzed by prenyl transferase. Squalene synthetase catalyzes the head-to-head addition of two achiral molecules of famesyl pyrophosphate, through a chiral cyclopropane intermediate, to form the achiral triterpene, squalene (75). 

Processes affecting the carbon-isotopic compositions of isoprenoid lipids. The isoprene carbon skeleton is indicated schematically in Figure 27. The corresponding biosynthetic reactant—equivalent in its role to acetyl-CoA—is isopentenyl pyrophosphate. As shown in Figure 29, this compound can be made by two different and fully independent pathways. The mevalonic-acid pathway was until recently thought to be the only route to isoprenoids. The deoxyxylulose-phosphate, or methylerythritol-phosphate, pathway was first discovered in Bacteria by Rohmer and coworkers (Flesch and Rohmer... 

Precursor selection An important step in designing a microbial labeling process is the identification of one or more suitable labeled precursors. Generally, secondary metabolites are biosynthesized via primary metabolites from five metabolic sources. These are amino acids, shikimic acid (shikimic acid pathway), acetate and its homologues (polyketide pathway), mevalonic acid (isoprene pathway) and carbohydrates. Selection of a suitable precursor is primarily influenced by the biosynthetic pathway(s) involved, but also depends on the desired position of label in the product and the availability of labeled precursors. 

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