Overexpression of functional human oxidosqualene cyclase in Escherichia coli

Selective and brain-penetrant lanosterol synthase inhibitors target glioma stem-like cells by inducing 24(S),25-epoxycholesterol production

Glioblastoma (GBM) is an aggressive adult brain cancer with few treatment options due in part to the challenges of identifying brain-penetrant drugs. Here, we investigated the mechanism of MM0299, a tetracyclic dicarboximide with anti-glioblastoma activity. MM0299 inhibits lanosterol synthase (LSS) and diverts sterol flux away from cholesterol into a "shunt" pathway that culminates in 24(S),25-epoxycholesterol (EPC). EPC synthesis following MM0299 treatment is both necessary and sufficient to block the growth of mouse and human glioma stem-like cells by depleting cellular cholesterol. MM0299 exhibits superior selectivity for LSS over other sterol biosynthetic enzymes. Critical for its application in the brain, we report an MM0299 derivative that is orally bioavailable, brain-penetrant, and induces the production of EPC in orthotopic GBM tumors but not normal mouse brain. These studies have implications for the development of an LSS inhibitor to treat GBM or other neurologic indications.

Modification of isoprene synthesis to enable production of curcurbitadienol synthesis in Saccharomyces cerevisiae

Cucurbitane-type triterpenoids such as mogrosides and cucurbitacins that are present in the plants of Cucurbitaceae are widely used in Asian traditional medicine. Cucurbitadienol is the skeleton of cucurbitane-type triterpenoids. As an alternative production strategy, we developed baker's yeast Saccharomyces cerevisiae as a microbial host for the eventual transformation of cucurbitadienol. The synthetic pathway of cucurbitadienol was constructed in Saccharomyces cerevisiae by introducing the cucurbitadienol synthase gene from different plants, resulting in 7.80 mg cucurbitadienol from 1 L of fermentation broth. Improving supplies of isoprenoid precursors was then investigated for increasing cucurbitadienol production. Cucurbitadienol production increased to 21.47 mg/L through the overexpression of a global regulatory factor (UPC2) gene of triterpenoid synthase. In addition, knockout of the ERG7 gene increased cucurbitadienol production from 21.47 to 61.80 mg/L. Finally, fed-batch fermentation was performed, and 63.00 mg/L cucurbitadienol was produced. This work is an important step towards the total biosynthesis of valuable cucurbitane-type triterpenoids and demonstrates the potential for developing a sustainable and secure yeast biomanufacturing platform for triterpenoids.

Design strategies of oxidosqualene cyclase inhibitors: Targeting the sterol biosynthetic pathway

Targeting the sterol biosynthesis pathway has been explored for the development of new bioactive compounds. Among the enzymes of this pathway, oxidosqualene cyclase (OSC) which catalyzes lanosterol cyclization from 2,3-oxidosqualene has emerged as an attractive target. In this work, we reviewed the most promising OSC inhibitors from different organisms and their potential for the development of new antiparasitic, antifungal, hypocholesterolemic and anticancer drugs. Different strategies have been adopted for the discovery of new OSC inhibitors, such as structural modifications of the natural substrate or the reaction intermediates, the use of the enzyme's structural information to discover compounds with novel chemotypes, modifications of known inhibitors and the use of molecular modeling techniques such as docking and virtual screening to search for new inhibitors. This review brings new perspectives on structural insights of OSC from different organisms and reveals the broad structural diversity of OSC inhibitors which may help evidence lead compounds for further investigations with various therapeutic applications.

β-Amyrin biosynthesis: catalytic mechanism and substrate recognition

In the past five years, there have been remarkable advances in the study of β-amyrin synthase. This review outlines the catalytic mechanism and substrate recognition in β-amyrin biosynthesis, which have been attained by the site-directed mutagenesis and substrate analog experiments.

Squalene-hopene cyclases-evolution, dynamics and catalytic scope

Herein we highlight recent mechanistic findings on the impact of solvent dynamics on catalysis displayed by squalene-hopene cyclases (SHCs). These fascinating biocatalysts that appeared early during the evolution of terpene biosynthetic machineries exploit a catalytic aspartic acid donating the anti-oriented proton to the terminal CC double bond of pre-folded isoprenoid substrates. We review how the unusual strength of this Brønsted acid can be used to harness a plethora of non-natural protonation-driven reactions in a plastic enzyme fold. Moreover, recent results underline how the reaction termination by deprotonation or water addition is governed by the spatial location of water in the active site. Site-directed mutagenesis of amino acids located in the hydrophobic binding pocket allows for the generation of novel catalytic function by active site reshaping with relatively small enzyme libraries. A deepened understanding of triterpene cyclase dynamics in concert with chemical expertise thus have a great potential to allow for the biocatalytic manufacturing of tailored building bricks that would expand the chemical repertoire currently found in nature.

Unraveling Entropic Rate Acceleration Induced by Solvent Dynamics in Membrane Enzymes

Enzyme catalysis evolved in an aqueous environment. The influence of solvent dynamics on catalysis is, however, currently poorly understood and usually neglected. The study of water dynamics in enzymes and the associated thermodynamical consequences is highly complex and has involved computer simulations, nuclear magnetic resonance (NMR) experiments, and calorimetry. Water tunnels that connect the active site with the surrounding solvent are key to solvent displacement and dynamics. The protocol herein allows for the engineering of these motifs for water transport, which affects specificity, activity and thermodynamics. By providing a biophysical framework founded on theory and experiments, the method presented herein can be used by researchers without previous expertise in computer modeling or biophysical chemistry. The method will advance our understanding of enzyme catalysis on the molecular level by measuring the enthalpic and entropic changes associated with catalysis by enzyme variants with obstructed water tunnels. The protocol can be used for the study of membrane-bound enzymes and other complex systems. This will enhance our understanding of the importance of solvent reorganization in catalysis as well as provide new catalytic strategies in protein design and engineering.