2024-03-29T12:17:41Z
https://niigata-u.repo.nii.ac.jp/oai
oai:niigata-u.repo.nii.ac.jp:00001560
2022-12-15T03:34:14Z
453:454
485:486:487
Site-directed mutagenesis experiments on the putative deprotonation site of squalene-hopene cyclase from Alicyclobacillus acidocaldarius.
Sato, Tsutomu
Kouda, Masanori
Hoshino, Tsutomu
squalene
terpene cyclase
triterpene
To provide insight into the catalytic mechanism for the final deprotonation reaction of squalene-hopene cyclase (SHC) from Alicyclobacillus acidocaldarius, mutagenesis experiments were conducted for the following ten residues: Thr41, Glu45, Glu93, Arg127, Trp133, Gln262, Pro263, Tyr267, Phe434 and Phe437. An X-ray analysis of SHC has revealed that two types of water molecules ("front water" and "back waters") were involved around the deprotonation site. The results of these mutagenesis experiments allow us to propose the functions of these residues. The two residues of Gln262 and Pro263 probably work to keep away the isopropyl group of the hopanyl cation intermediate from the "front water molecule," that is, to place the "front water" in a favorable position, leading to the minimal production of by-products, i.e., hopanol and hop-21(22)-ene. The five residues of Thr41, Glu45, Glu93, Arg127 and Trp133, by which the hydrogen-bonded network incorporating the "back waters" is constructed, increase the polarization of the "front water" to facilitate proton elimination from the isopropyl moiety of the hopanyl cation, leading to the normal product, hop-22(29)-ene. The three aromatic residues of Tyr267, Phe434 and Phe437 are likely to play an important role in guiding squalene from the enzyme surface to the reaction cavity (substrate channeling) by the strong affinity of their aromatic residues to the squalene substrate.
Japan Society for Bioscience, Biotechnology, and Agrochemistry
2004
eng
journal article
VoR
http://hdl.handle.net/10191/6338
https://niigata-u.repo.nii.ac.jp/records/1560
http://doi.org/10.1271/bbb.68.728
AA10824164
0916-8451
Bioscience, Biotechnology, and Biochemistry
68
3
728
738
https://niigata-u.repo.nii.ac.jp/record/1560/files/07_0014.pdf
application/pdf
186.7 kB
2019-07-29