Ryousuke Ito

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The function of the active-site residues of oxidosqualene cyclases (OSCs) has been presumed mainly in light of the product distribution; however, not much research has been performed into the enzymatic activity of mutated OSCs. β-Amyrin, which is widely found in the plant kingdom, is classified as an OSC; mutational studies on β-amyrin cyclase are very(More)
The gene products of AK121211, AK066327, and AK070534 from Oryza sativa encode cycloartenol, parkeol, and achilleol B synthases, respectively. Parkeol synthase is a unique enzyme that affords parkeol as a single product. Achilleol B synthase is the third seco-type triterpene cyclase identified to date, and triterpenes produced by this synthase include(More)
Many of the functions of the active site residues in β-amyrin synthase and its catalytic mechanism remain unclear. Herein, we examined the functions of the highly conserved Phe413, Tyr259, and Trp257 residues in the β-amyrin synthase of Euphorbia tirucalli. The site-specific mutants F416V and F416M showed nearly the same enzymatic activities as the wild(More)
Correction for 'β-Amyrin synthase from Euphorbia tirucalli L. functional analyses of the highly conserved aromatic residues Phe413, Tyr259 and Trp257 disclose the importance of the appropriate steric bulk, and cation-π and CH-π interactions for the efficient catalytic action of the polyolefin cyclization cascade' by Ryousuke Ito et al., Org. Biomol. Chem.,(More)
The effect of the steric volume at C-19 of (3S)-2,3-oxidosqualene 1 on the polycyclization reaction by β-amyrin synthase was examined. The substrate analogs, in which the methyl group at C-19 of 1 was substituted by an ethyl group and hydrogen atom, were converted into the following three new compounds: (17β-H, 20S)-20-ethyl-dammara-12,24-diene 9, β-amyrin(More)
β-Amyrin, a triterpene, is widely distributed in plants and its glycosides confer important biological activities. Mutagenesis studies on β-amyrin synthase are very limited as compared with those of squalene-hopene cyclase and lanosterol synthase. This study was conducted to elucidate the function of the F474 residue of Euphorbia tirucalli β-amyrin cyclase,(More)
β-Amyrin, a natural triterpene, is widely distributed in the plant kingdom, and its pentacyclic skeleton is produced by oxidosqualene cyclase (OSC). OSC enzymes are classified as membrane proteins, and they catalyze the polycyclization reaction of (3S)-2,3-oxidosqualene to yield nearly 150 different cyclic triterpene skeletons. To date, no report has(More)
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