Isoprene biosynthesis

Isoprene (2-methyl 1,3-butadiene, Fig. 2) is the simplest terpenoid produced by many plants, and is produced abundantly by some tree species such as poplars. The mechanism of isoprene biosynthesis is a straightforward diphosphate ionization of... 

Fig. 1. Hipothesis of two interacting carboxylation systems in isoprens releasing plant photosynthesis. Designations BC - pool of reactions of Benson-Calvin cycle AcCoA - pool of acetyl-CoA and isoprene biosynthesis RUBPC/O-ribulosebisphsphate C/0 X-C-unknown carboxylase leading to acetyl-CoA biosyynthesis PGA-phosphoglyceric acid PGAL- phosphoglyceric aldehyde GA-D,L-glyceraldehyde a,b,c...n-alternative pathways of acetyl-CoA use.

The main consumers of the formed molecules are commonly assumed to be the reactions, leading to the primary products of photosynthesis, including the predecessor of isoprene biosynthesis. 

The capability of PTR-MS to detect stable isotopes is potentially a very useful tool to study the biological pathways in relation to plant volatiles. A well-studied example is the formation of C-isoprene (CsHg) during C02 fumigation, demonstrating the linkage between photosynthesis and isoprene emission in intact leaves from oak and cottonwood [16]. Despite the fact that the biochemistry of isoprene formation is known, the role of isoprene biosynthesis in plants is stiU not clear, especially in its relation to photosynthetic precursors in leaf chloroplasts. 

Hoffmann GF, Gibson KM, Brandt IK, Bader PI, Wappner RS, Sweetman L. Mevalonic aciduria - an inborn error of cholesterol and non-sterol isoprene biosynthesis. New Eng J Med 1986 314 1610. 

There are two naturally occurring pathways for isoprene biosynthesis the meval-onate (MVA) pathway and the methylerythritol 4-phosphate (MEP) pathway... 

The scale-up fermentation of bioisoprene by engineered E. coli is summarized in Table 16.2. In these scale-up studies, suitable control of the fermentation process is essential for isoprene production due to the toxicity of the accumulating intermediate metabolites (GPP, FPP, IPP, DMAPP, MVPP). The accumulation of these intracellular metabolites can inhibit the growth of the hosts as well as its feedback inhibition on MVK. Therefore, a significant rate of isoprene biosynthesis cannot be reached or maintained for a long time under these conditions. In order... 

The logical design of the central metabolic pathway is vital for the commercial production of isoprene, as well as the precursor of isoprene biosynthesis derived from an important intermediate component in the central metabolic pathway (acetyl-CoA for MVA, Pyr and G3P for MEP). First, the central metabolic pathway should be reasonably designed to provide an optimal flux of precursors for the biosynthesis of isoprene in a balanced ratio and without carbon loss. Second, the strategies for the rational design of the central metabolic pathway should be different from the biosynthesis pathway of isoprene. 

The ED pathway can be engineered for isoprene production via the MEP pathway, which can provide the balanced ratio of Pyr and G3P to increase the productivity of isoprene. EMP in tandem with the MEP pathway is commonly used for isoprene biosynthesis in E. coli. However, the highest isoprene production and yield were achieved from ED pathway, which were 3 and 6 times higher than those of EMP [72]. This is because imbalanced distribution of Pyr and G3P existed in... 

Lv, X., Xie, W., Lu, W., Guo, F. et al. (2014) Enhanced isoprene biosynthesis in Saccharomyces cerevisiae by engineering of the native acetyl-CoA and mevalonic acid pathways with a push-pull-restrain strategy. /. Biotechnol,... 

Loivamaki, M., Louis, S., Cinege, G. et al. (2007) Circadian rhythms of isoprene biosynthesis in grey poplar leaves. Plant Physiol. 143, 540. 

Schnitzler, J. P, Graus, M., Kreuzwieser, J. et al. (2004) Contribution of different carbon sources to isoprene biosynthesis in poplar leaves. Plant Physiol. 135, 152. Brilli, F., Ruuskanen, T. M., Schnitzhofer, R. ef a/. (2011) Detection of plant volatiles after leaf wounding and darkening by Proton Transfer Reaction Time-of-Hight Mass Spectrometry (PTR-TOF). PLoS ONE. 6, 1. 

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