3.3- Dimethylallyl pyrophosphate

Isopentenyl pyrophosphate undergoes an enzyme catalyzed reaction that converts It m an equilibrium process to 3 methyl 2 butenyl pyrophosphate (dimethylallyl pyrophosphate)... 

Isopentenyl pyrophosphate and dimethylallyl pyrophosphate are structurally sim liar—both contain a double bond and a pyrophosphate ester unit—but the chemical reactivity expressed by each is different The principal site of reaction m dimethylallyl pyrophosphate is the carbon that bears the pyrophosphate group Pyrophosphate is a reasonably good leaving group m nucleophilic substitution reactions especially when as in dimethylallyl pyrophosphate it is located at an allylic carbon Isopentenyl pyrophosphate on the other hand does not have its leaving group attached to an allylic carbon and is far less reactive than dimethylallyl pyrophosphate toward nucleophilic reagents The principal site of reaction m isopentenyl pyrophosphate is the carbon-carbon double bond which like the double bonds of simple alkenes is reactive toward electrophiles... 

The chemical properties of isopentenyl pyrophosphate and dimethylallyl pyrophosphate are complementary m a way that permits them to react with each other to form a carbon-carbon bond that unites two isoprene units Using the tt electrons of its double... 

Geranyl pyrophosphate is an allylic pyrophosphate and like dimethylallyl pyrophosphate can act as an alkylating agent toward a molecule of isopentenyl pyrophosphate A 15 carbon carbocation is formed which on deprotonation gives/ar nesyl pyrophosphate... 

The conversion of isopentenyl diphosphate (IPP) to terpenoids begins with its isomerization to dimethylallyl diphosphate, abbreviated DMAPP and formerly called dimethylallyl pyrophosphate. These two C5 building blocks then combine to give the C10 unit geranyl diphosphate (GPP). The corresponding alcohol, geraniol, is itself a fragrant terpenoid that occurs in rose oil. 

During the second step, mevalonic acid is implicated in a number of enzymic reactions involving ATP, and is converted to isopentyl pyrophosphate and to its isomer 3,3-dimethylallyl pyrophosphate. Actually, the two compounds constitute the active isoprene , which... 

ARIGONI, D., EISENREICH, W, LATZEL, C., SAGNER, S., RADYKEWICZ, T, ZENK, M.H., BACHER, A., Dimethylallyl pyrophosphate is not the committed precursor of isopentenyl pyrophosphate during terpenoid biosynthesis from 1-deoxyxylulose in higher plants, Proc. Natl. Acad. Sci. USA, 1999, 96,1309-1314. 

Chrysanthemic acid (1) consists of ten carbons, suggesting that it is a monoterpene. The cyclopropane ring of the acid moiety is a feature of pyrethrins. Rivera et al. isolated chrysanthemyl pyrophosphate synthase (CPPase or alternatively referred to as chrysanthemyl diphosphate synthase) underlying the formation of chrysanthemyl pyrophosphate (16) containing a cyclopropane ring from two molecules of dimethylallyl pyrophosphate (15) (DMAPP) and the gene thereof [21]. They found that the reaction involves the cF-2-3 cyclopropanation of DMAPPs in a non-head-to-tail manner. 

This enzyme [EC 5.3.3.2] catalyzes the interconversion of isopentenyl pyrophosphate and dimethylallyl pyrophosphate. 

The formation of phytoalexins such as glyceollins and phaseollins requires C-prenylation by a range of pterocarpan prenyltransferase (PTP) activities, with dimethylallyl pyrophosphate (DMAPP) as the prenyl donor. For glyceollins and phaseollins, prenylation occurs at position C-2 or C-4 of glycinol or C-10 of 3,9-dihydroxypterocarpan. ° ° However, there are differing activities in other species. For example, in Lupinus albus (white lupin) a prenyltransferase acting at the C-6, -8, and -3 positions of isoflavones has been identified.PTPs have also been characterized in detail for the formation of prenylated flavanones in Sophora flavescens (see, e.g., Ref. 207). However, no cDNA clones for flavonoid-related prenyltransferases have been published to date. 

Stage (J) Condensation of Six Activated Isoprene Units to Form Squalene Isopentenyl pyrophosphate and dimethylallyl pyrophosphate now undergo a head-to-tail condensation, in which one pyrophosphate group is displaced and a 10-carbon chain, geranyl pyrophosphate, is formed (Fig. 21-36). (The head is the end to which pyrophosphate is joined.) Geranyl pyrophosphate undergoes another head-to-tail condensation with isopentenyl pyro-... 

Cholesterol is formed from acetyl-CoA in a complex series of reactions, through the intermediates /3-hydroxy-/3-methylglutaryl-CoA, mevalonate, and two activated isoprenes, dimethylallyl pyrophosphate and isopentenyl pyrophosphate. Condensation of isoprene units produces the noncyclic squalene, which is cyclized to yield the steroid ring system and side chain. 

The steroid hormones (glucocorticoids, mineralocorticoids, and sex hormones) are produced from cholesterol by alteration of the side chain and introduction of oxygen atoms into the steroid ring system. In addition to cholesterol, a wide variety of isoprenoid compounds are derived from mevalonate through condensations of isopentenyl pyrophosphate and dimethylallyl pyrophosphate. 

The principal steps in the mechanism of polyisoprene formation in plants are known and should help to improve the natural production of hydrocarbons. Mevalonic acid, a key intermediate derived from plant carbohydrate via acetylcoenzyme A, is transformed into isopentenyl pyrophosphate (IPP) via phosphorylation, dehydration, and decarboxylation (see Alkaloids). IPP then rearranges to dimethylallyl pyrophosphate (DMAPP). DMAPP and... 

Example condensation of dimethylallyl pyrophosphate with isopentenyl pyrophosphate)... 

Dihydroxyproline 80 Diiron desaturases 863 Diiron oxygenases 863 Diiron proteins 862-864 Diiron-tyrosinate proteins 862-863 Diisopropylfluorophosphate (DFP, diisopropylphosphofluoridate) 610s Dimethylallyl diphosphate 712s Dimethylallyl pyrophosphate, condensation of 527... 

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