scholarly journals Biosynthesis of geraniol and nerol and their β-d-glucosides in Perlargonium graveolens and Rosa dilecta

1972 ◽  
Vol 130 (4) ◽  
pp. 1045-1054 ◽  
Author(s):  
Derek V. Banthorpe ◽  
Geoffrey N. J. Le Patourel ◽  
Martin J. O. Francis
Keyword(s):  
Double Bond ◽  
Hydrogen Atom ◽  
Higher Plants ◽  
Animal Tissue ◽  
Labelling Pattern ◽  
Isopentenyl Pyrophosphate ◽  
Pelargonium Graveolens ◽  
Dimethylallyl Pyrophosphate

1. 3R-[2-14C]Mevalonate was incorporated into geranyl and neryl β-d-glucosides in petals of Rosa dilecta in up to 10.6% yield, and the terpenoid part was specifically and equivalently labelled in the moieties derived from isopentenyl pyrophosphate and 3,3-dimethylallyl pyrophosphate. A similar labelling pattern, with incorporations of 0.06–0.1% was found for geraniol or nerol formed in leaves of Pelargonium graveolens The former results provide the best available evidence for the mevalonoid route to regular monoterpenes in higher plants. 2. Incorporation studies with 3RS-[2-14C,(4R)-4-3H1]-mevalonate and its (4S)-isomer showed that the pro-4R hydrogen atom of the precursor was retained and the pro-4S hydrogen atom was eliminated in both alcohols and both glucosides. These results suggest that the correlation of retention of the pro-4S hydrogen atom of mevalonate with formation of a cis-substituted double bond, such as has been found in certain higher terpenoids, does not apply to the biosynthesis of monoterpenes. It is proposed that either nerol is derived from isomerization of geraniol or the two alcohols are directly formed by different prenyltransferases. Possible mechanisms for these processes are discussed. 3. The experiments with [14C,3H]mevalonate also show that in these higher plants, as has been previously found in animal tissue and yeast, the pro-4S hydrogen atom of mevalonate was lost in the conversion of isopentenyl pyrophosphate into 3,3-dimethylallyl pyrophosphate.

scholarly journals Mechanistic and stereochemical studies on 3-oxo steroid Δ4-Δ5-isomerase from human placenta

1980 ◽  
Vol 185 (2) ◽  
pp. 411-421 ◽  
Author(s):  
M Akhtar ◽  
M Calder ◽  
T Smith ◽  
J N Wright
Keyword(s):  
Double Bond ◽  
Hydrogen Atom ◽  
Human Placenta ◽  
Microsomal Fraction ◽  
Isomerization Reaction ◽  
Acidic Group ◽  
Incoming Proton ◽  
Membrane Bound ◽  
Hydroxy Steroid ◽  
Steroid Dehydrogenase

The mechanism of isomerization of delta 5-3-ox steroids to delta 4-3-oxo steroids was examined by using the membrane-bound 3-oxo steroid delta 4-delta 5-isomerase (EC 5.3.3.1) and the 3 beta-hydroxy steroid dehydrogenase present in the microsomal fraction obtained from full-term human placenta. (1) Methods for the preparation of androst-5-ene-3 beta, 17 beta-diol specifically labelled at the 4 alpha-, 4 beta- or 6-positions are described. (2) Incubations with androst-5-ene-3 beta, 17 beta-diol stereospecifically 3H-labelled either in the 4 alpha- or 4 beta-position showed that the isomerization reaction occurs via a stereospecific elimination of the 4 beta hydrogen atom. In addition, the complete retention of 3H in the delta 4-3-oxo steroids obtained from [4 alpha-3H]androst-5-ene-3 beta, 17 beta-diol indicates that the non-enzymic contribution to these experiments was negligible. (3) To study the stereochemistry of the insertion of the incoming proton at C-6, the [6-3H]androst-4-ene-3, 17-dione obtained from the oxidation isomerization of [6-3H]androst-5-ene-3 beta, 17 beta-diol was enzymically hydroxylated in the 6 beta-position by the fungus Rhizopls stolonifer. Retention of 3H in the 6 alpha-position of the isolated 6 beta-hydroxyandrost-4-ene-3, 17-dione indicates that in the isomerase-catalysed migration of the C(5) = C(6) double bond, the incoming proton from the acidic group on the enzyme must enter C-6 from the beta-face, forcing the existing 3H into the 6 alpha-position.

Photolyse du butène-1 dans l'ultraviolet à vide

1973 ◽  
Vol 51 (17) ◽  
pp. 2853-2859 ◽  
Author(s):  
Guy J. Collin
Keyword(s):  
Double Bond ◽  
Hydrogen Atom ◽  
Kinetic Energy ◽  
Thermal Energy ◽  
Hydrogen Atoms ◽  
Excited Molecules

The vacuum u.v. photolysis of 1 -butene was studied in the 147–105 nm region. The main products formed from the fragmentation of excited molecules are allene, 1,3-and 1,2-butadienes, ethylene, and acetylene. The addition of a hydrogen atom to the double bond produces mainly secondary butyl radicals (91%) at 147 nm. At 123.6 nm, this proportion becomes 82%. Thus at shorter wavelengths (10 and 11.6–11.8 eV), hydrogen atoms are produced with a kinetic energy higher than the thermal energy.

scholarly journals The isoprenoid alcohol pathway, a synthetic route for isoprenoid biosynthesis

2019 ◽  
Vol 116 (26) ◽  
pp. 12810-12815 ◽  
Author(s):  
James M. Clomburg ◽  
Shuai Qian ◽  
Zaigao Tan ◽  
Seokjung Cheong ◽  
Ramon Gonzalez
Keyword(s):  
Energy Efficient ◽  
Sole Carbon Source ◽  
Isoprenoid Biosynthesis ◽  
High Flux ◽  
Alternative Route ◽  
Synthetic Route ◽  
Isopentenyl Pyrophosphate ◽  
Commodity Chemicals ◽  
Central Carbon ◽  
Dimethylallyl Pyrophosphate

The more than 50,000 isoprenoids found in nature are all derived from the 5-carbon diphosphates isopentenyl pyrophosphate (IPP) and dimethylallyl pyrophosphate (DMAPP). Natively, IPP and DMAPP are generated by the mevalonate (MVA) and 2-C-methyl-d-erythritol-4-phosphate (MEP) pathways, which have been engineered to produce compounds with numerous applications. However, as these pathways are inherently constrained by carbon, energy inefficiencies, and their roles in native metabolism, engineering for isoprenoid biosynthesis at high flux, titer, and yield remains a challenge. To overcome these limitations, here we develop an alternative synthetic pathway termed the isoprenoid alcohol (IPA) pathway that centers around the synthesis and subsequent phosphorylation of IPAs. We first established a lower IPA pathway for the conversion of IPAs to isoprenoid pyrophosphate intermediates that enabled the production of greater than 2 g/L geraniol from prenol as well as limonene, farnesol, diaponeurosporene, and lycopene. We then designed upper IPA pathways for the generation of (iso)prenol from central carbon metabolites with the development of a route to prenol enabling its synthesis at more than 2 g/L. Using prenol as the linking intermediate further facilitated an integrated IPA pathway that resulted in the production of nearly 0.6 g/L total monoterpenoids from glycerol as the sole carbon source. The IPA pathway provides an alternative route to isoprenoids that is more energy efficient than native pathways and can serve as a platform for targeting a repertoire of isoprenoid compounds with application as high-value pharmaceuticals, commodity chemicals, and fuels.

scholarly journals Development of the activities of enzymes of the isoprenoid pathway during early stages of pea-seed germination

1972 ◽  
Vol 130 (4) ◽  
pp. 983-995 ◽  
Author(s):  
T. R. Green ◽  
D. J. Baisted
Keyword(s):  
Seed Germination ◽  
Initial Increase ◽  
Mevalonate Kinase ◽  
Isopentenyl Pyrophosphate ◽  
Isoprenoid Pathway ◽  
Dimethylallyl Pyrophosphate ◽  
Rate Limiting ◽  
Pea Seed ◽  
Germination Stage ◽  
Squalene Synthetase

The activities of individual enzymes of the isoprenoid pathway from mevalonate kinase to squalene synthetase in homogenates of seeds germinated up to 32h were assayed. Changes in the activity of each enzyme were observed and compared with the activity at the 2h germination stage. Activities of alkaline phosphatase and fructose 1,6-diphosphate aldolase were similarly measured to provide a reference for changes in the general metabolic activity of seeds during imbibition of water. Water uptake reached a plateau after 12h. The reference enzymes almost doubled in activity between 2 and 8h and thereafter their activities steadily declined. All of the enzymes of the isoprenoid pathway increased in activity between 2 and 6h and, thereafter, with the exception of the prenyltransferase, their activities remained relatively constant. With the prenyltransferase activity the initial increase was followed by a short plateau between 6 and 9h and then a second increase to a maximum between 14 and 16h. After 16h the activity declined. The relative activities of the isoprenoid enzymes at 16h of germination were mevalonate kinase>phosphomevalonate kinase>pyrophosphomevalonate decarboxylase≈isopentenyl pyrophosphate isomerase>squalene synthetase>isopentenyl pyrophosphate/dimethylallyl pyrophosphate prenyltransferase. The finding that the prenyltransferase may be the rate-limiting enzyme in squalene synthesis from mevalonate is discussed in relation to regulation of isoprenoid synthesis during pea-seed germination.

scholarly journals QM/MM studies of the type II isopentenyl diphosphate–dimethylallyl diphosphate isomerase demonstrate a novel role for the flavin coenzyme

RSC Advances ◽  
2017 ◽  
Vol 7 (36) ◽  
pp. 22286-22293
Author(s):  
Qianqian Hou ◽  
Kang Wang ◽  
Feng Xu ◽  
Wenshen Zhang ◽  
Kejian Ji ◽  
...  
Keyword(s):  
Isopentenyl Diphosphate ◽  
Type Ii ◽  
Isopentenyl Pyrophosphate ◽  
Dimethylallyl Diphosphate ◽  
Dimethylallyl Pyrophosphate

The type II isopentenyl diphosphate:dimethylallyl diphosphate isomerase (IDI-2) catalyzes the reversible isomerization of isopentenyl pyrophosphate (IPP) and dimethylallyl pyrophosphate (DMAPP).

Mechanism of the double bond isomerization from Δ24(28) to Δ24(25) in sitosterol biosynthesis in higher plants

1999 ◽  
Vol 40 (50) ◽  
pp. 8863-8866 ◽  
Author(s):  
Tatsuya Okuzumi ◽  
Noriyuki Hara ◽  
Yoshinori Fujimoto
Keyword(s):  
Double Bond ◽  
Higher Plants ◽  
Double Bond Isomerization

scholarly journals Novel pathways of oleic and cis -vaccenic acid biosynthesis by an enzymatic double-bond shifting reaction in higher plants

FEBS Letters ◽  
1990 ◽  
Vol 264 (2) ◽  
pp. 228-230 ◽  
Author(s):  
Akira Shibahara ◽  
Kohei Yamamoto ◽  
Mariko Takeoka ◽  
Akemi Kinoshita ◽  
Goro Kajimoto ◽  
...  
Keyword(s):  
Double Bond ◽  
Higher Plants ◽  
Vaccenic Acid ◽  
Acid Biosynthesis

Markovnikov free radical addition reactions, a sleeping beauty kissed to life

2016 ◽  
Vol 45 (3) ◽  
pp. 577-583 ◽  
Author(s):  
Reinhard W. Hoffmann
Keyword(s):  
Free Radical ◽  
Double Bond ◽  
Hydrogen Atom ◽  
Sleeping Beauty ◽  
Radical Addition ◽  
Addition Reactions ◽  
Free Radical Addition

This review covers free radical additions, which are initiated by the formal addition of a hydrogen atom to a CC double bond.

Sign in / Sign up

Export Citation Format

Share Document