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Literature summary extracted from

  • Hoshino, T.; Nakano, S.; Kondo, T.; Sato, T.; Miyoshi, A.
    Squalene-hopene cyclase: final deprotonation reaction, conformational analysis for the cyclization of (3R,S)-2,3-oxidosqualene and further evidence for the requirement of an isopropylidene moiety both for initiation of the polycyclization cascade and for the formation of the 5-membered E-ring (2004), Org. Biomol. Chem., 2, 1456-1470.
    View publication on PubMed

Protein Variants

EC Number Protein Variants Comment Organism
4.2.1.129 P263A the mutation results in a greatly enhanced production of hopanol along with the decreased formation of hopene. A high production of hopanol would be explained as follows. The point mutations could give rise to the perturbation around the “front water”. This disordered “front water” cannot correctly act as the catalytic base for the deprotonation reaction to form hopene, and in turn could be placed near to the final hopanyl cation, leading to a high production of hopanol without forming hopene Alicyclobacillus acidocaldarius
4.2.1.129 P263G the mutation results in a greatly enhanced production of hopanol along with the decreased formation of hopene. A high production of hopanol would be explained as follows. The point mutations could give rise to the perturbation around the “front water”. This disordered “front water” cannot correctly act as the catalytic base for the deprotonation reaction to form hopene, and in turn could be placed near to the final hopanyl cation, leading to a high production of hopanol without forming hopene Alicyclobacillus acidocaldarius
4.2.1.129 Q262A the mutation results in a greatly enhanced production of hopanol along with the decreased formation of hopene. A high production of hopanol would be explained as follows. The point mutations could give rise to the perturbation around the “front water”. This disordered “front water” cannot correctly act as the catalytic base for the deprotonation reaction to form hopene, and in turn could be placed near to the final hopanyl cation, leading to a high production of hopanol without forming hopene Alicyclobacillus acidocaldarius
4.2.1.129 Q262G the mutation results in a greatly enhanced production of hopanol along with the decreased formation of hopene. A high production of hopanol would be explained as follows. The point mutations could give rise to the perturbation around the “front water”. This disordered “front water” cannot correctly act as the catalytic base for the deprotonation reaction to form hopene, and in turn could be placed near to the final hopanyl cation, leading to a high production of hopanol without forming hopene Alicyclobacillus acidocaldarius

Natural Substrates/ Products (Substrates)

EC Number Natural Substrates Organism Comment (Nat. Sub.) Natural Products Comment (Nat. Pro.) Rev. Reac.
4.2.1.129 hopan-22-ol Alicyclobacillus acidocaldarius
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 squalene + H2O
-
 ?

Organism

EC Number Organism UniProt Comment Textmining
4.2.1.129 Alicyclobacillus acidocaldarius
-
-
-

Substrates and Products (Substrate)

EC Number Substrates Comment Substrates Organism Products Comment (Products) Rev. Reac.
4.2.1.129 hopan-22-ol
-
 Alicyclobacillus acidocaldarius squalene + H2O
-
 ?
4.2.1.129 hopan-22-ol squalene–hopene cyclase from prokaryotes catalyses the conversion of the acyclic molecule of squalene into the pentacyclic triterpenes of hopene and hopanol in the the ratio 5:1. The polycyclization of squalene to hopene consists of sequential ring-forming reaction steps. The polycyclization cascade is initiated by the electrophilic attack of the acidic proton, donated by the DXDD motif, to one of the two terminal double bonds. The polycyclization reaction is quenched by proton elimination from the alternative terminal methyl group of squalene. Based on the X-ray analysis of Alicyclobacilus acidocaldarius, the catalytic base responsible for the deprotonation reaction has been suggested to be a water molecule (named a front water), the polarization of which is enhanced by other waters (named back waters) that construct the hydrogen-bonding network by a combination of seven residues T41, E45, E93, R127, Q262, W133 and Y267. The front water thus polarized can store the proton generated from either Me-29 or Me-30 of hopanyl cation to form hopene, but hopanol is produced if the front water adds as hydroxyl to the C-22 cation of the A-ring instead of accepting the proton Alicyclobacillus acidocaldarius squalene + H2O
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 ?

Synonyms

EC Number Synonyms Comment Organism
4.2.1.129 squalene-hopene cyclase ambiguous Alicyclobacillus acidocaldarius