Site-directed mutagenesis of conserved aromatic residues in rat squalene epoxidase

Abe, Ikuro; Abe, Tsuyoshi; Lou, Weiwei; Masuoka, Takayoshi; Noguchi, Hiroshi

doi:10.1016/j.bbrc.2006.11.014

Cited by 29 publications

(26 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Only terminal double bonds of squalene are oxidized to 2,3-oxidosqualene and 2,3:22,23-dioxidosqualene subsequently. 5,6-Oxidosqualene and 10,11-oxidosqualene are not observed in the reaction catalyzed by SE (van Duuren and Schmitt , 1960 ;Abe et al , 2007 ). Oxidation of the terminal double bonds is characteristic for other enzymatic reactions (Lucas et al , 2010 ).…”

Section: Specifi City Of Epoxidation Reactionmentioning

confidence: 90%

“…The activity of enzyme towards squalene analogs was also checked (Abe et al , 2007 ). A lack of one double bond (5,6-dihydrosqualene, 10,11-dihydrosqualene) as well as two double bonds (6,7,18,19-tetrahydrosqualene, 10,11,14,15-tetrahydrosqualene) of squalene do not preclude epoxidation of terminal isoprene units (Figure 2 ).…”

Section: Specifi City Of Epoxidation Reactionmentioning

confidence: 99%

“…Conserved aromatic residues, through π -π interactions, help in the correct folding of the π -electron rich, hydrophobic substrate, and in this way affi rms the regio-and stereospecifi city of an epoxidation reaction. Analysis of a series of single amino acid mutants of rats ' squalene monooxygenase obtained for evaluation of the enzyme activity showed that almost all of them were less active than the wild-type enzyme (Abe et al , 2007 ).…”

Section: Structure-activity Relationshipmentioning

confidence: 99%

See 2 more Smart Citations

Squalene monooxygenase – a target for hypercholesterolemic therapy

Belter¹,

Skupińska²,

Giel-Pietraszuk

et al. 2011

BCHM

View full text Add to dashboard Cite

Squalene monooxygenase catalyzes the epoxidation of C-C double bond of squalene to yield 2,3-oxidosqualene, the key step of sterol biosynthesis pathways in eukaryotes. Sterols are essential compounds of these organisms and squalene epoxidation is an important regulatory point in their synthesis. Squalene monooxygenase downregulation in vertebrates and fungi decreases synthesis of cholesterol and ergosterol, respectively, which makes squalene monooxygenase a potent and attractive target of hypercholesterolemia and antifungal therapies. Currently some fungal squalene monooxygenase inhibitors (terbinafi ne, naftifi ne, butenafi ne) are in clinical use, whereas mammalian enzymes ' inhibitors are still under investigation. Research on new squalene monooxygenase inhibitors is important due to the prevalence of hypercholesterolemia and the lack of both suffi cient and safe remedies. In this paper we (i) review data on activity and the structure of squalene monooxygenase, (ii) present its inhibitors, (iii) compare current strategies of lowering cholesterol level in blood with some of the most promising strategies, (iv) underline advantages of squalene monooxygenase as a target for hypercholesterolemia therapy, and (v) discuss safety concerns about hypercholesterolemia therapy based on inhibition of cellular cholesterol biosynthesis and potential usage of squalene monooxygenase inhibitors in clinical practice. After many years of use of statins there is some clinical evidence for their adverse effects and only partial effectiveness. Currently they are drugs of choice but are used with many restrictions, especially in case of children, elderly patients and women of childbearing potential. Certainly, for the next few years, statins will continue to be a suitable tool for cost-effective cardiovascular prevention; however research on new hypolipidemic drugs is highly desirable. We suggest that squalene monooxygenase inhibitors could become the hypocholesterolemic agents of the future.

show abstract

Section: Specifi City Of Epoxidation Reactionmentioning

confidence: 90%

Section: Specifi City Of Epoxidation Reactionmentioning

confidence: 99%

Section: Structure-activity Relationshipmentioning

confidence: 99%

See 1 more Smart Citation

Squalene monooxygenase – a target for hypercholesterolemic therapy

Belter¹,

Skupińska²,

Giel-Pietraszuk

et al. 2011

BCHM

View full text Add to dashboard Cite

show abstract

“…6B), suggesting that a truncated sqe1-3 protein missing the C-terminal ϳ100 amino acids might accumulate in sqe1-3 plants. The missing region in sqe1-3 is the region in rat ERG1 that includes four cysteine residues and several aromatic residues that are important for enzyme activity (41,42), sug-FIGURE 8. Elongation defects of sqe1-3.…”

Section: Discussionmentioning

confidence: 99%

Arabidopsis thaliana Squalene Epoxidase 1 Is Essential for Root and Seed Development

Rasbery¹,

Shan

LeClair³

et al. 2007

Journal of Biological Chemistry

109

View full text Add to dashboard Cite

Squalene epoxidase converts squalene into oxidosqualene, the precursor of all known angiosperm cyclic triterpenoids, which include membrane sterols, brassinosteroid phytohormones, and non-steroidal triterpenoids. In this work, we have identified six putative Arabidopsis squalene epoxidase (SQE) enzymes and used heterologous expression in yeast to demonstrate that three of these enzymes, SQE1, SQE2, and SQE3, can epoxidize squalene. We isolated and characterized Arabidopsis sqe1 mutants and discovered severe developmental defects, including reduced root and hypocotyl elongation. Adult sqe1-3 and sqe1-4 plants have diminished stature and produce inviable seeds. The sqe1-3 mutant accumulates squalene, consistent with a block in the triterpenoid biosynthetic pathway. Therefore, SQE1 function is necessary for normal plant development, and the five SQE-like genes remaining in this mutant are not fully redundant with SQE1.Plants are estimated to produce more than 500,000 secondary metabolites (1). These compounds have many functions, including attracting pollinators, communicating with neighboring plants, and defending against pathogens and herbivores (2, 3). The importance of secondary metabolites is highlighted by the extensive resources that plants invest in producing these compounds. Although once thought to be metabolically simple, more than 170 secondary metabolites have been identified in Arabidopsis thaliana (reviewed in Ref. 4).Triterpenoids are the 30-carbon subset of terpenoids, the largest class of secondary metabolites. Triterpenoid biosynthesis is diagramed in Fig. 1. Isopentenyl diphosphate and dimethylallyl diphosphate are synthesized from mevalonate and oligomerized to farnesyl diphosphate by farnesyl diphosphate synthase (FPS).5 Farnesyl diphosphate is dimerized to squalene by squalene synthase. Squalene epoxidase (SQE)-mediated oxidation then produces oxidosqualene, which triterpene synthases cyclize to Ͼ80 triterpene skeletons (5, 6). Further metabolism of these compounds produces membrane sterols, brassinosteroid phytohormones, saponins, other defense compounds, cuticular waxes, and numerous triterpenoids that have not been functionally characterized.The yeasts and mammals that have been investigated each encode a single squalene epoxidase. In contrast, several plants have multiple genes predicted to encode squalene epoxidases, a diversity suggesting that this step may be subject to additional or unique regulation in plants. Two Medicago truncatula SQE enzymes have been biochemically characterized (7). The Brassica napus (8), Populus trichocarpa, and Oryza sativa genomes each have multiple predicted SQE enzymes. Despite the likely importance of SQE to plant growth and development, no plant mutants with defects in these enzymes have been reported.In this work, we heterologously expressed the six Arabidopsis putative SQE enzymes in Saccharomyces cerevisiae lacking squalene epoxidase to determine which have squalene epoxidase activity. We isolated Arabidopsis sqe1 loss-of-function mutants and found t...

show abstract

“…1A): the dinucleotide-binding motif of GXGXXG, DG, and GD motifs, all of which are highly conserved among eukaryotic SEs. 15) These motifs are also found in the putative SE, but the GXGXXG motif was replaced by GXSXXG sequence. The membrane-spanning region, frequently found in those from yeasts and vertebrates, was lacking in the putative SE.…”

Section: Resultsmentioning

confidence: 99%