Chapter 1 Biosynthesis of cholesterol

Rilling, Hans C.; Chayet, L.

doi:10.1016/s0167-7306(08)60677-8

Cited by 16 publications

(13 citation statements)

References 89 publications

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“…3) in plants (Grunwald, 1975;Goodwin, 1985) and animals (Rilling and Chayet, 1985). The LKB gene may not be involved in this conversion because the lkb mutant and WT contained similar levels of cholesterol in their shoots, seeds, and microsomal membranes (Tables III and V).…”

Section: Br Deficiency In the Lkb Mutant Is Due To Impaired Synthesismentioning

confidence: 99%

Brassinosteroid/Sterol Synthesis and Plant Growth as Affected bylka and lkb Mutations of Pea1

et al. 1999

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The dwarf pea (Pisum sativum) mutants lka and lkb are brassinosteroid (BR) insensitive and deficient, respectively. The dwarf phenotype of the lkb mutant was rescued to wild type by exogenous application of brassinolide and its biosynthetic precursors. Gas chromatography-mass spectrometry analysis of the endogenous sterols in this mutant revealed that it accumulates 24-methylenecholesterol and isofucosterol but is deficient in their hydrogenated products, campesterol and sitosterol. Feeding experiments using 2 H-labeled 24-methylenecholesterol indicated that the lkb mutant is unable to isomerize and/or reduce the ⌬ 24(28) double bond. Dwarfism of the lkb mutant is, therefore, due to BR deficiency caused by blocked synthesis of campesterol from 24-methylenecholesterol. The lkb mutation also disrupted sterol composition of the membranes, which, in contrast to those of the wild type, contained isofucosterol as the major sterol and lacked stigmasterol. The lka mutant was not BR deficient, because it accumulated castasterone. Like some gibberellin-insensitive dwarf mutants, overproduction of castasterone in the lka mutant may be ascribed to the lack of a feedback control mechanism due to impaired perception/signal transduction of BRs. The possibility that castasterone is a biologically active BR is discussed.

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Section: Br Deficiency In the Lkb Mutant Is Due To Impaired Synthesismentioning

confidence: 99%

Brassinosteroid/Sterol Synthesis and Plant Growth as Affected bylka and lkb Mutations of Pea1

et al. 1999

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“…A possible candidate to be modified by prenylation is the viral protein encoded by the open reading frame L83L, which contains a carboxyl-terminal CTIL type I geranylgeranylation motif (35) and is transcribed at a late time of infection. 2 The use of drugs known to interfere with the prenylation of proteins may also help to understand the role, if any, of protein prenylation during the infectious cycle.…”

Section: Table Imentioning

confidence: 99%

“…Attempts to construct ASFV recombinants depleted of the trans-prenyltransferase gene have failed, 2 suggesting that the gene is essential for virus multiplication. A system for inducible gene expression from ASFV recombinants, recently developed in our laboratory (36), might be useful to investigate the role of the trans-prenyltransferase during virus replication.…”

Section: Table Imentioning

confidence: 99%

The African Swine Fever Virus Prenyltransferase Is an Integral Membrane trans-Geranylgeranyl-diphosphate Synthase

Alejo¹,

Andrés²,

Viñuela

et al. 1999

Journal of Biological Chemistry

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In a previous study, it was shown that the protein encoded by the gene B318L of African swine fever virus (ASFV) is a trans-prenyltransferase that catalyzes in vitro the condensation of farnesyl diphosphate and isopentenyl diphosphate to synthesize geranylgeranyl diphosphate and longer chain prenyl diphosphates (Alejo, A., Yá ñ ez, R. J., Rodríguez, J. M., Viñ uela, E., and Salas, M. L. (1997) J. Biol. Chem. 272, 9417-9423). To investigate the in vivo function of the viral enzyme, we have determined, in this work, its subcellular localization and activity in cell extracts. Two systems were used in these studies: cells infected with ASFV and cells infected with a recombinant pseudo-Sindbis virus carrying the complete B318L gene. In this latter system, the trans-prenyltransferase was found to colocalize with the endoplasmic reticulum marker protein-disulfide isomerase, whereas in cells infected with ASFV, the viral enzyme was present in cytoplasmic viral assembly sites, associated with precursor viral membranes derived from the endoplasmic reticulum. In addition, after subcellular fractionation, the viral enzyme partitioned into the membrane fraction. Extraction of membrane proteins with alkaline carbonate and Triton X-114 indicated that the ASFV enzyme behaved as an integral membrane protein. The membrane enzyme synthesized predominantly all-trans-geranylgeranyl diphosphate from farnesyl diphosphate and isopentenyl diphosphate. These results indicate that the viral B318L protein is a transgeranylgeranyl-diphosphate synthase, being the only enzyme of this type that is known to have a membrane localization.In the biosynthetic pathway of isoprenoid compounds, different enzymes belonging to the family of prenyltransferases catalyze the condensation of isopentenyl diphosphate (IPP) 1 with allylic diphosphates to give rise to prenyl diphosphates of different chain lengths and double-bond stereochemistry (1-3). Thus, farnesyl-diphosphate synthase and geranylgeranyldiphosphate synthase produce the 15-carbon all-trans-FPP and the 20-carbon all-trans-GGPP isoprenoids, respectively, which can serve as substrates for protein farnesylation or geranylgeranylation (4, 5). FPP is also the direct precursor for the synthesis of cholesterol and serves as allylic substrate for cisand trans-polyprenyl-diphosphate synthases involved in the synthesis of the long chain isoprenoids with cis-or trans-stereochemistry, which are the precursors of dolichols and the lateral chain of ubiquinones, respectively (6, 7).Prenyltransferases have been described in a wide variety of organisms, both prokaryotic and eukaryotic, where their isoprenoid products play essential roles in cellular processes. More recently, it has been shown that prenylation of cellular or viral proteins is required for the multiplication of certain viruses (8 -11). In this connection, we have previously reported (12) the characterization of the first viral trans-prenyltransferase encoded by African swine fever virus (ASFV), a large enveloped DNA virus with an icosahedral morp...

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“…Steroidal demethylation at C-14 in yeast, rat, and plants is known to proceed via C-14 hydroxymethyl and C-14 aldehyde (Goodwin 1985, Rilling andChayet 1985). The removal of two sterol C-4 methyl groups proceeds stepwise oxidation of the methyl group to a carboxyl group (Goodwin 1985, Rilling andChayet 1985).…”

mentioning

confidence: 99%

“…The removal of two sterol C-4 methyl groups proceeds stepwise oxidation of the methyl group to a carboxyl group (Goodwin 1985, Rilling andChayet 1985). Thus, C-26 demethylation of BRs is expected to be formed via intermediates with C-26 being a hydroxymethyl, aldehyde or carboxyl group.…”

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confidence: 99%

Regulation of castasterone level in primary roots of maize, Zea mays

Kim

Chang

et al. 2006

Physiologia Plantarum

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Gas chromatography-mass spectrometry analysis revealed that primary roots of maize contain 28-norcastasterone (28-norCS) and its biosynthetic precursors, cholesterol, and cholestanol, which suggests that the C 27 -brassinosteroid (C 27 -BR) biosynthetic pathway to generate 28-norCS is operative in the roots. A cell-free enzyme solution prepared from maize roots successfully mediated C24-methylation of 28-norCS to produce castasterone (CS) with the aid of S-adenosyl-L-methionine, which indicates that CS can be generated through C 27 -BR biosynthesis, as well as C 28 -BR biosynthesis, in maize roots. Enzymatic conversion study using the cell-free enzyme solution demonstrated that CS is converted into 26-norCS in the enzyme solution. Exogenously applied 28-norCS and 26-norCS showed less activity than CS in the activation of gravitropic curvature and inhibition of root elongation. Taken together, a steady-state level of CS, the active BR in maize roots, seems to be strictly controlled by complicated processes such as C 28 -and C 27 -BR biosynthesis and biodegradation by C26-demethylation to exert its biological activity.

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Chapter 1 Biosynthesis of cholesterol

Cited by 16 publications

References 89 publications

Brassinosteroid/Sterol Synthesis and Plant Growth as Affected bylka and lkb Mutations of Pea1

Brassinosteroid/Sterol Synthesis and Plant Growth as Affected bylka and lkb Mutations of Pea1

The African Swine Fever Virus Prenyltransferase Is an Integral Membrane trans-Geranylgeranyl-diphosphate Synthase

Regulation of castasterone level in primary roots of maize, Zea mays

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