Consequences of Microbial Interactions with Hydrocarbons, Oils, and Lipids: Production of Fuels and Chemicals by Sang Yup Lee

Author:Sang Yup Lee
Language: eng
Format: epub, pdf
Publisher: Springer International Publishing, Cham

2.2 Isoprene Biosynthesis Pathway

Regardless of the emitting organisms, the universal precursors for biosynthesis of all isoprenoids including isoprene are isopentenyldiphosphate (IPP) and dimethylallyl diphosphate (DMAPP), the formation of which can be accomplished by two distinct and independent pathways, the methylerythritol-phosphate (MEP) pathway [also known as the 1-deoxy-d-xylulose-5-phosphate (DXP) pathway] and the mevalonate (MVA) pathway (Fig. 2). The MEP pathway initiates with condensation of glyceraldehyde-3-phosphate (G-3-P) and pyruvate to form DXP, which is then converted into MEP and further modified to yield hydroxy-2-methyl-2-butenyl-4-diphosphate (HMBPP), the substrate for IPP formation. The MEP pathway is present in most bacteria, cyanobacteria, green microalgae, and plant plastids (Xue and Ahring 2011). On the other hand, the MVA pathway is responsible for isoprenoid synthesis in eukaryotes, archaea, and cytosol of higher plants (Miziorko 2011). Acetyl-CoA is the primary feedstock for the MVA pathway, three molecules of which are condensed to form 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA). The subsequent reduction product mevalonate is often used as a node to divide the MVA pathway into an “upper section” and a “lower section.” Mevalonate is then converted to IPP via phosphorylation and decarboxylation.

Fig. 2Isoprene biosynthesis via MEP pathway (blue arrows) or MVA pathway (red arrows). Gene symbols and the enzymes encoded: dxs DXP synthase, dxr DXP reduction isomerase, ispD DXP-ME synthase, ispE CDP-ME kinase, ispF MECPP synthase, ispG HMBPP synthase, ispH HMBPP reductase, idi or IDI IPP isomerase, ERG10 acetyl-coA acetyl transferase, HMGS HMG-CoA synthase, HMGR HMG-CoA reductase, MK mevalonate kinase, PMK mevalonate-5-phosphate kinase, MVD mevalonate-5-diphosphate decarboxylase, ispS isoprene synthase. Pathways: CBB Calvin–Benson–Bassham cycle, EMP Embden–Meyerhof pathway, EDP Entner–Doudoroff pathway, PPP pentose phosphate pathway. Pathway intermediates: G-3-P glyceraldehyde-3-phosphate, DXP 1-deoxy-d-xylulose 5-phosphate, MEP 2-C-methyl-d-erythritol 4-phosphate, CDP-ME 4-diphosphocytidyl-2-C-methyl-d-erythritol, CDP-MEP 4-diphosphocytidyl-2-C-methyl-d-erythritol 2-phosphate, MECPP 2-C-methyl-d-erythritol 2,4-cyclopyrophosphate, HMBPP 1-hydroxy-2-methyl-2-(E)-butenyl 4-pyrophosphate, IPP isopentenyl pyrophosphate, DMAPP dimethylallyl pyrophosphate, Ac-CoA acetyl-CoA, AcAc-CoA acetoacetyl-CoA, HMG-CoA 3-hydroxy-3-methylglutaryl coenzyme A, MVA mevalonate, PMev mevalonate 5-phosphate, PPMev mevalonate pyrophosphate (Modified after Ye et al. 2016)

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