Isopentenyl pyrophosphate isomerase

Shelton, D.A., Leach, D.N., and Henry, R.J., Isopentenyl pyrophosphate isomerases from Melaleuca altemifolia (Cheel) and their role in isoprenoid biosynthesis, J. Hort. 

Phytoene synthase [EC 2.5.1.32] (also known as gera-nylgeranyl-diphosphate geranylgeranyltransferase and prephytoene-diphosphate synthase) catalyzes the reaction of two geranylgeranyl diphosphate to produce pyrophosphate (or, diphosphate) and prephytoene diphosphate. Isopentenyl pyrophosphate isomerase [EC 5.3.3.2] catalyzes the interconversion of isopentenyl diphosphate and dimethylallyl diphosphate. See also Geranylgeranyl Diphosphate Geranylgeranyltransferase... 

Blanc, V.M. and Pichersky, E. (1995) Nucleotide sequence of a Clarkia breweri cDNA clone of ipil, a gene encoding isopentenyl pyrophosphate isomerase. Plant Physiol, 108, 855-6. 

Dogbo, O. and Camara, B. (1987) Rurification of isopentenyl pyrophosphate isomerase and geranylgeranyl pyrophosphate synthase from Capsicum chromoplasts by affinity chromatography. Biochim. Biophys. Acta, 920, 140-8. 

Spurgeon, S.L., Sathyamoorthy, N. and Porter, J.W. (1984) Isopentenyl pyrophosphate isomerase and prenyltransferase from tomato fruit plastids. Arc/ . Biochem. Biophys., 230, 446-54. 

Two isoenzymes of isopentenyl pyrophosphate isomerase (EC 5.3.3.2) were found by Ogura et in pumpkin. These workers also studied farnesyl pyrophosphate synthetase (EC 2.5.1.1) from this plant in an attempt to define... 

Isopentenyl pyrophosphate is next converted to its isomer dimethylallylpy-rophosphate by isopentenyl pyrophosphate isomerase. (A CH2=CH—CH2— group on an organic molecule is sometimes referred to as an allyl group.)... 

Isopentenyl pyrophosphate isomerase catalyzes the equilibrium between the and bi double bonds of a 3-methylbutenyl pyrophosphate (Fig. 7). This is the first enzyme in the biosynthesis of allylic pyrophosphates and is a cytoplasmic protein that has been detected in many tissues. Initial purification was reported from yeast [45] and a subsequent purification to homogeneity has been reported with pig Ever as the source of protein [46]. There are some variances in the apparent molecular weight of this protein. One group [46] reported a molecular weight of 85 000 while we found 22000 to be the value for the enzyme from the same source [47]. There is... 

Fig. 11.3 Simplified diagram of isoprenoid metabolic pathway relative to the conversions among carotenoids that have been genetically manipulated. Enzymes catalysing some key reactions are indicated by the following abbreviations IPI, isopentenyl pyrophosphate isomerase PSY, phytoene synthase PDS, phytoene desaturase (crti, gene from Erwinia uredovora) ZDS, -carotene desaturase LCYB, lycopene / -cyclase CRTR-b, /3-carotene 3,3 -hydroxylase CCS, capsanthin-capsombin synthase CRTO, /3-carotene ketolase.

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). 

Mevalonate is then converted to an isoprenoid unit by a combination of phosphorylation, decarboxylation, and dephosphorylation reactions (Figure 21.28). Three successive reactions, each of which is catalyzed by an enzyme that requires ATP, give rise to isopentenyl pyrophosphate, a five-carbon isoprenoid derivative. Isopentenyl pyrophosphate and dimethylallyl pyrophosphate, another isoprenoid derivative, can be interconverted in a rearrangement reaction catalyzed by the enzyme isopentenyl pyrophosphate isomerase. 

ALBRECHT, M., SANDMANN, G., Light-stimulated carotenoid biosynthesis during transformation of maize etioplasts is regulated by increased activity of isopentenyl pyrophosphate isomerase.. Plant Physiol. 1994,105,529-534. 

Cholesterol synthesis Hydroxymetylglutaryl-CoA reductase Mevalonate kinase Isopentenyl pyrophosphate isomerase... 

Figure 2.11. Lipid synthesis. GDP = glycerol-3-phosphate dehydrogenase. PP = phosphat-idate phosphatase. CPT=choline phosphotransferase. BPT= ethanolamine phosphotransferase. AC = acetyl CoA carboxylase. HAD 3-hydroxyacyl-CoA dehydrogenase. CCPT = cemmide choline phosphotransferase. HMGR = hydroxymethyl utaryl-CoA reductase. MK = mevalonate kinase. IPPI = isopentenyl pyrophosphate isomerase...

The isomerization of isopentenyl diphosphate to dimethylallyl diphosphate is catalyzed by the enzyme isopentenyl pyrophosphate isomerase. In this process, the 2R hydrogen is lost and another hydrogen is picked up on the opposite face. Thus, the original methyl group is now cis or (Z)- to the methylene bearing the diphosphate group, that is. 

Fig. 56.2 Carotenoid biosynthesis pathway in plants. Enzymes (with abbreviations) indicated are isopentenyl pyrophosphate isomerase (IPI), geranylgeranyl pyrophosphate synthase (GGPS), phytoene synthase (PSY), phytoene desaturase (PDS), zeta-carotene desaturase (ZDS), carotenoid isomerase (CRTISO), lycopene beta-cyclase (LCYB), lycopene epsilon-cyclase (LCYE), beta-ring carotene hydroxylase (CHXB), epsilon-ring carotene hydroxylase (CHXE), zeaxanthin epoxidase (ZEP), violaxanthin de-epoxidase (VDE), capsorubin-capsanthin synthase (CCS), neoxanthin synthase (NXS), 9-cis epoxycarotenoid dioxygenase (NCED), and carotenoid cleavage dioxygenase (CCD). (Source [101], drawn using KeGG pathway)...

Although, terpenoids show enormous chemical and structural diversity, their backbones are synthesized from only two universal precursors isopentenyl pyrophosphate (IPP) and its highly electrophilic allyUc isomer dimethylaUyl pyrophosphate (DMAPP) [25]. IPP is isomerized to DMAPP by the enzyme isopentenyl pyrophosphate isomerase. The mevalonate pathway for the biosynthesis of terpenoids has been illustrated in Fig. 86.3. To summarize, the active isoprene unit (IPP) is repetitively added to DMAPP or a prenyl diphosphate in sequential head-to-tail... 

The condensation of dimethyallyl pyrophosphate, an isomerization product of isopentenyl pyrophosphate, with isopentenyl pyrophosphate, has been shown to yield geranyl pyrophosphate (Lynen et al., 1959). The enzyme, isopentenyl pyrophosphate isomerase, has been described (Agranoff et al., 1960). Geranyl pyrophosphate may condense with another molecule of isopentenyl pyrophosphate to yield farnesyl pyrophosphate. The enzyme farnesyl synthetase had been isolated by Lynen et al. (1959). The reductive dimerization of two molecules of... 

Reardon, JE, Abeles RH. Mechanism of action of isopentenyl pyrophosphate isomerase Evidence for a carbonium ion intermediate. Biochemistry-USA, 1986 25 5609-5616. 

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