The ubiquinone coenzyme Q (CoQ) is synthesized in mitochondria with a
large, hydrophobic isoprenoid side chain. It functions in mitochondrial res-piration as well as protecting membranes from oxidative damage. Yeast
that cannot synthesize CoQ (DCoQ) are viable, but cannot grow on nonfer-mentable carbon sources, unless supplied with ubiquinone.
2C-Methyl-d-erythritol-4-phosphate synthase, encoded by the ispC gene
(also designated dxr), catalyzes the first committed step in the nonmevalo-nate isoprenoid biosynthetic pathway. The reaction involves the isomeriza-tion of 1-deoxy-d-xylulose 5-phosphate, giving a branched-chain aldose
derivative that is subsequently reduced to 2C-methyl-d-erythritol 4-phos-phate.
In the nonmevalonate pathway of isoprenoid biosynthesis,
the conversion of 2C-methyl-D-erythritol 4-phosphate into
its cyclic diphosphate proceeds via nucleotidyl intermediates
and is catalyzed by the products of theispD,ispE andispF
genes. An open reading frame of Campylobacter jejuni
with similarity to theispDandispFgenes ofEscherichia coli
was cloned into an expression vector directing the formation
of a 42 kDa protein in a recombinantE. colistrain.
TheispC gene of Arabidopsis thalianawas expressed in pseudomature
form without the putative plastid-targeting sequence in a recombinant
Escherichia colistrain. The recombinant protein was purified by affinity
chromatography and was shown to catalyze the formation of 2C-methyl-d-erythritol 4-phosphate from 1-deoxy-d-xylulose 5-phosphate at a rate of
(kcat 4.4 s
). The Michaelis constants for 1-deoxy-d-xylulose 5-phosphate and the cosubstrate NADPH are 132 and 30lm,
The homodimeric 2C-methyl-d-erythritol 4-phosphate cytidylyltransferase
contributes to the nonmevalonate pathway of isoprenoid biosynthesis. The
crystal structure of the catalytic domain of the recombinant enzyme derived
from the plant Arabidopsis thalianahas been solved by molecular replace-ment and refined to 2.0 A˚
Tocopherol (tocos = con cháu, pherol = sinh ra) khá phổ biến ở cây xanh, rau xà lách, hạt ngũ cốc, dầu thực vật, gan bò, lòng đỏ trứng. Nhóm tocopherol gồm 8 hợp chất, bao gồm vòng 8 chromanol và một chuỗi bên isoprenoide Sản phẩm cuối cùng của quá trình sinh tổng hợp là -tocopherol (5,7,8-
Ubiquinone is an essential factor for the electron transfer system and is
also a known lipid antioxidant. The length of the ubiquinone isoprenoid
side-chain differs amongst living organisms, with six isoprene units in the
budding yeastSaccharomyces cerevisiae, eight units in Escherichia coliand
10 units in the fission yeast Schizosaccharomyces pombeand in humans.
The carbon backbones of Z,E-mixed isoprenoids are synthesized by
sequentialcis-condensation of isopentenyl diphosphate (IPP) and an allylic
diphosphate through actions of a series of enzymes calledcis-prenyltrans-ferases. Recent molecular analyses of Micrococcus luteusB-P 26 undecapre-
An open reading frame (Acc. no. P50740) on theBacillus
subtilis chromosome extending from bp 184 997–186 043
with similarity to theidi-2 gene ofStreptomycessp. CL190
specifying type II isopentenyl diphosphate isomerase was
expressed in a recombinant Escherichia colistrain. The
recombinant protein with a subunit mass of 39 kDa was
purified to apparent homogeneity by column chromatog-raphy. The protein was shown to catalyse the conversion of
dimethylallyl diphosphate into isopentenyl diphosphate and
vice versa at rates of 0.23 and 0.
The isoprenoid methyl farnesoate (MF) has been implicated in the regulation of crustacean development and reproduction in conjunction with eyestalk molt inhibiting hormones and ecdysteroids. Farnesoic acid O-methyltransferase (FAMeT) catalyzes the methylation of farnesoic acid (FA) to produce MF in the terminal step of MF synthesis. We have previously cloned and characterized the shrimp FAMeT. In the present study, recombinant FAMeT (rFAMeT) was produced for bioassay and antiserum generation.
In this chapter you will understand: What is lipit? Structural properties of 2 major classes of lipids, know the functions of the major classes of acyl-lipids, know the functions of the major classes of isoprenoids (steroids, carotenoids/chlorophyll, lipid vitamins, ubiquinone/plastoquinone),...
In chapter 9 (part 2), you will know that isoprenoids are derived from 5 carbon isoprene units that can condense in a head to head or head to tail manner to make a large array of isoprenoid compounds; know the general ring structure of a steroid molecule; know the general functions of common steroids (Cholesterol, steroid hormones); know general functions of membranes; know properties and components of the fluid mosaic model for biological membranes.
In this chapter, students will be able to: Know the reactions/enzymes/intermediates/co-substrates/co-factor/structures involved in the synthesis of IPP from the mevalonate pathway; know how HMG-CoA reductase is regulated, know the similarities and differences between IPP synthesis and ketone body synthesis, know the similarities and differences between IPP synthesis and ketone body synthesis.
In the apicoplast of apicomplexan parasites, plastidic-type ferredoxin and
reductase (FNR) form a short electron transport chain
that provides reducing power for the synthesis of isoprenoid precursors.
These proteins are attractive targets for the development of novel drugs
against diseases such as malaria, toxoplasmosis, and coccidiosis.
Proteins are covalently modified with a variety of lipids, including fatty
acids, isoprenoids, and cholesterol. Lipid modifications play important
roles in the localization and function of proteins. The focus of this review
is S-palmitoylation, the reversible addition of palmitate and other long-chain fatty acids to proteins at cysteine residues in a variety of sequence
Human Brox is a newly identified 46 kDa protein that has a Bro1 domain-like sequence and a C-terminal thioester-linkage site of isoprenoid lipid
(CAAX motif) (C standing for cysteine, A for generally aliphatic amino
acid, and X for any amino acid).
The isoprenoid chain of ubiquinone (Q) is determined bytrans-polyprenyl
diphosphate synthase in micro-organisms and presumably in mammals.
Because mice and humans produce Q9 and Q10
, they are expected to pos-sess solanesyl and decaprenyl diphosphate synthases as the determining
enzyme for a type of ubiquinone.
The 1-deoxyxylulose 5-phosphate reductoisomerase (DXR,
EC22.214.171.1247)catalyzes the conversionof 1-deoxy-D-xylulose
5-phosphate (DXP)into 2-C-methyl-D-erythritol 4-phos-phate (MEP). This transformation is a two-step process
involving a rearrangement of DXP into the putative inter-mediate 2-C-methyl-D-erythrose 4-phosphate followed by a
NADPH-dependent reduction of the latter aldehyde. By
C]DXP as a substrate, the rearrangement of DXP
C]2-C-methyl-D-erythrose 4-phosphate was shown
to be NADPH dependent, although it does not involve
a reduction step. ...