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Analysis of the Catalytic Mechanism of Bifunctional Triterpene/Sesquarterpene Cyclase: Tyr167 Functions To Terminate Cyclization of Squalene at the Bicyclic Step
Author(s) -
Tenkovskaia Liudmila,
Murakami Mizuki,
Okuno Kotone,
Ueda Daijiro,
Sato Tsutomu
Publication year - 2017
Publication title -
chembiochem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.05
H-Index - 126
eISSN - 1439-7633
pISSN - 1439-4227
DOI - 10.1002/cbic.201700329
Subject(s) - bicyclic molecule , squalene , triterpene , cyclase , stereochemistry , bifunctional , chemistry , substrate (aquarium) , catalysis , terpene , enzyme , organic chemistry , biology , medicine , ecology , alternative medicine , pathology
Onoceroids are a group of triterpenes biosynthesized from squalene or dioxidosqualene by cyclization from both termini. We previously identified a bifunctional triterpene/sesquarterpene cyclase (TC) that constructs a tetracyclic scaffold from tetraprenyl‐β‐curcumene (C 35 ) but a bicyclic scaffold from squalene (C 30 ) in the first reaction. TC also accepts the bicyclic intermediate as a substrate and generates tetracyclic and pentacyclic onoceroids in the second reaction. In this study, we analyzed the catalytic mechanism of an onoceroid synthase by using mutated enzymes. TC Y167A produced an unnatural tricyclic triterpenol, but TC Y167L , TC Y167F , and TC Y167W formed small quantities of tricyclic compounds, which suggested that the bulk size at Y167 contributed to termination of the cyclization of squalene at the bicyclic step. Our findings provide insight into the unique catalytic mechanism of TC, which triggers different cyclization modes depending on the substrate. These findings may facilitate the large‐scale production of an onoceroid for which natural sources are limited.