A Single Residue Switch Converts Abietadiene Synthase into a Pimaradiene Specific Cyclase

Terpene synthases often catalyze complex cyclization reactions that typically represent the committed step in particular biosynthetic pathways, leading to great interest in their enzymatic mechanisms. We have recently demonstrated that substitution of a specific Ile with Thr was sufficient to “short circuit” the complex cyclization reaction normally catalyzed by ent-kaurene synthases to instead produce ent-pimaradiene. Here we report that the complex cyclization/rearrangement reaction catalyzed by abietadiene synthase can be similarly cut short to produce pimaradienes by an analogous Ser for Ala change, albeit with a slight shift in active site location to accommodate the difference in substrate stereochemistry. This result has mechanistic implications for enzymatic catalysis of abietadiene cyclization, and terpene synthases more broadly. Furthermore, these defined single residue switches may be useful in engineering product outcome in diterpene synthases more generally

A Modular Approach for Facile Biosynthesis of Labdane-Related Diterpenes

Labdane-related diterpenoids are a large group of over 5,000 natural products whose biosynthesis typically proceeds through a labdadienyl/copalyl diphosphate (CPP) intermediate to a further cyclized and/or rearranged hydrocarbon diterpene en route to more elaborated compounds. Here we report a modular approach for facile biosynthesis of labdane-related diterpenes wherein base pGGxC vectors capable of introducing bacterial production of any one of the three common stereoisomers of CPP can be co-introduced with diterpene synthases that convert these CPP intermediates to specific diterpene hydrocarbon skeletal structures. The utility of this approach is demonstrated by individually engineering E. coli to produce any one of eight different diterpene skeletal structures, which collectively serve as precursors to literally thousands of distinct natural products

Structure-Function Analysis of Mammalian CYP2B Enzymes Using 7-Substituted Coumarin Derivatives as Probes: Utility of Crystal Structures and Molecular Modeling in Understanding Xenobiotic Metabolism s

ABSTRACT Crystal structures of CYP2B35 and CYP2B37 from the desert woodrat were solved in complex with 4-(4-chlorophenyl)imidazole (4-CPI). The closed conformation of CYP2B35 contained two molecules of 4-CPI within the active site, whereas the CYP2B37 structure demonstrated an open conformation with three 4-CPI molecules, one within the active site and the other two in the substrate access channel. To probe structurefunction relationships of CYP2B35, CYP2B37, and the related CYP2B36, we tested the O-dealkylation of three series of related substrates-namely, 7-alkoxycoumarins, 7-alkoxy-4-(trifluoromethyl)coumarins, and 7-alkoxy-4-methylcoumarinswith a C1-C7 side chain. CYP2B35 showed the highest catalytic efficiency (k cat /K M ) with 7-heptoxycoumarin as a substrate, followed by 7-hexoxycoumarin. In contrast, CYP2B37 showed the highest catalytic efficiency with 7-ethoxy-4-(trifluoromethyl) coumarin (7-EFC), followed by 7-methoxy-4-(trifluoromethyl) coumarin (7-MFC). CYP2B35 had no dealkylation activity with 7-MFC or 7-EFC. Furthermore, the new CYP2B-4-CPI-bound structures were used as templates for docking the 7-substituted coumarin derivatives, which revealed orientations consistent with the functional studies. In addition, the observation of multiple -Cl and -NH-p interactions of 4-CPI with the aromatic side chains in the CYP2B35 and CYP2B37 structures provides insight into the influence of such functional groups on CYP2B ligand binding affinity and specificity. To conclude, structural, computational, and functional analysis revealed striking differences between the active sites of CYP2B35 and CYP2B37 that will aid in the elucidation of new structure-activity relationships

GPCRomics : GPCR Expression in Cancer Cells and Tumors Identifies New, Potential Biomarkers and Therapeutic Targets

Financial support for these studies was provided by Roche, the Lymphoma and Leukemia Society, Friends of ANCHOR, an ASPET Astellas Award and grants from the National Institutes of Health, National Cancer Institute (CA189477, CA121938, CA155620). National Cancer Institute (NCI) Therapeutic Training Grant 5T32CA121938, NIH/NCI Research Grants R21 CA189477, an ASPET David Lehr Award and the Padres Pedal the Cause #PTC2017 award.Peer reviewedPublisher PD

Design and baseline characteristics of the finerenone in reducing cardiovascular mortality and morbidity in diabetic kidney disease trial

Background: Among people with diabetes, those with kidney disease have exceptionally high rates of cardiovascular (CV) morbidity and mortality and progression of their underlying kidney disease. Finerenone is a novel, nonsteroidal, selective mineralocorticoid receptor antagonist that has shown to reduce albuminuria in type 2 diabetes (T2D) patients with chronic kidney disease (CKD) while revealing only a low risk of hyperkalemia. However, the effect of finerenone on CV and renal outcomes has not yet been investigated in long-term trials. Patients and Methods: The Finerenone in Reducing CV Mortality and Morbidity in Diabetic Kidney Disease (FIGARO-DKD) trial aims to assess the efficacy and safety of finerenone compared to placebo at reducing clinically important CV and renal outcomes in T2D patients with CKD. FIGARO-DKD is a randomized, double-blind, placebo-controlled, parallel-group, event-driven trial running in 47 countries with an expected duration of approximately 6 years. FIGARO-DKD randomized 7,437 patients with an estimated glomerular filtration rate >= 25 mL/min/1.73 m(2) and albuminuria (urinary albumin-to-creatinine ratio >= 30 to <= 5,000 mg/g). The study has at least 90% power to detect a 20% reduction in the risk of the primary outcome (overall two-sided significance level alpha = 0.05), the composite of time to first occurrence of CV death, nonfatal myocardial infarction, nonfatal stroke, or hospitalization for heart failure. Conclusions: FIGARO-DKD will determine whether an optimally treated cohort of T2D patients with CKD at high risk of CV and renal events will experience cardiorenal benefits with the addition of finerenone to their treatment regimen. Trial Registration: EudraCT number: 2015-000950-39; ClinicalTrials.gov identifier: NCT02545049

A Single Residue Switch Converts Abietadiene Synthase into a Pimaradiene Specific Cyclase

Terpene synthases often catalyze complex cyclization reactions that typically represent the committed step in particular biosynthetic pathways, leading to great interest in their enzymatic mechanisms. We have recently demonstrated that substitution of a specific Ile with Thr was sufficient to “short circuit” the complex cyclization reaction normally catalyzed by ent-kaurene synthases to instead produce ent-pimaradiene. Here we report that the complex cyclization/rearrangement reaction catalyzed by abietadiene synthase can be similarly cut short to produce pimaradienes by an analogous Ser for Ala change, albeit with a slight shift in active site location to accommodate the difference in substrate stereochemistry. This result has mechanistic implications for enzymatic catalysis of abietadiene cyclization, and terpene synthases more broadly. Furthermore, these defined single residue switches may be useful in engineering product outcome in diterpene synthases more generally.This article is published as A Single Residue Switch Converts Abietadiene Synthase into a Pimaradiene Specific Cyclase, P. Ross Wilderman and and Reuben J. Peters, Journal of the American Chemical Society 2007 129 (51), 15736-15737, DOI: 10.1021/ja074977g. This article is made available under ACS AuthorChoice.</p

Following evolution's lead to a single residue switch for diterpene synthase product outcome

There have been few insights into the biochemical origins of natural product biosynthesis from primary metabolism. Of particular interest are terpene synthases, which often mediate the committed step in particular biosynthetic pathways so that alteration of their product outcome is a key step in the derivation of novel natural products. These enzymes also catalyze complex reactions of significant mechanistic interest. Following an evolutionary lead from two recently diverged, functionally distinct diterpene synthase orthologs from different subspecies of rice, we have identified a single residue that can switch product outcome. Specifically, the mutation of a conserved isoleucine to threonine that acts to convert not only the originally targeted isokaurene synthase into a specific pimaradiene synthase but also has a much broader effect, which includes conversion of the ent-kaurene synthases found in all higher plants for gibberellin phytohormone biosynthesis to the production of pimaradiene. This surprisingly facile switch for diterpene synthase catalytic specificity indicates the ease with which primary (gibberellin) metabolism can be subverted to secondary biosynthesis and may underlie the widespread occurrence of pimaradiene-derived natural products. In addition, because this isoleucine is required for the mechanistically more complex cyclization to tetracyclic kaurene, whereas substitution with threonine “short-circuits” this mechanism to produce the “simpler” tricyclic pimaradiene, our results have some implications regarding the means by which terpene synthases specify product outcome

Rice Contains Two Disparate ent-Copalyl Diphosphate Synthases with Distinct Metabolic Functions

Rice (Oryza sativa) produces ent-copalyl diphosphate for both gibberellin (GA) phytohormone and defensive phytoalexin biosynthesis, raising the question of how this initial biosynthetic step is carried out for these distinct metabolic processes. Here, a functional genomics approach has been utilized to identify two disparate ent-copalyl diphosphate synthases from rice (OsCPS1ent and OsCPS2ent). Notably, it was very recently demonstrated that only one of these (OsCPS1ent) normally operates in GA biosynthesis as mutations in this gene result in severely impaired growth. Evidence is presented here strongly indicating that the other (OsCPS2ent) is involved in related secondary metabolism producing defensive phytochemicals. In particular, under appropriate conditions, OsCPS2ent mRNA is specifically induced in leaves prior to production of the corresponding phytoalexins. Thus, transcriptional control of OsCPS2ent seems to be an important means of regulating defensive phytochemical biosynthesis. Finally, OsCPS1ent is significantly more similar to the likewise GA-specific gene An1/ZmCPS1ent in maize (Zea mays) than its class II terpene synthase paralogs involved in rice secondary metabolism. Hence, we speculate that this cross-species conservation by biosynthetic process reflects derivation of related secondary metabolism from the GA primary biosynthetic pathway prior to the early divergence between the separate lineages within the cereal/grass family (Poaceae) resulting in modern rice and maize.This article is published as Prisic, Sladjana, Meimei Xu, P. Ross Wilderman, and Reuben J. Peters. "Rice contains two disparate ent-copalyl diphosphate synthases with distinct metabolic functions." Plant physiology 136, no. 4 (2004): 4228-4236. doi: 10.1104/pp.104.050567. Copyright American Society of Plant Biologists. Posted with permission.</p

Rice Contains Two Disparate ent-Copalyl Diphosphate Synthases with Distinct Metabolic Functions

Rice (Oryza sativa) produces ent-copalyl diphosphate for both gibberellin (GA) phytohormone and defensive phytoalexin biosynthesis, raising the question of how this initial biosynthetic step is carried out for these distinct metabolic processes. Here, a functional genomics approach has been utilized to identify two disparate ent-copalyl diphosphate synthases from rice (OsCPS1(ent) and OsCPS2(ent)). Notably, it was very recently demonstrated that only one of these (OsCPS1(ent)) normally operates in GA biosynthesis as mutations in this gene result in severely impaired growth. Evidence is presented here strongly indicating that the other (OsCPS2(ent)) is involved in related secondary metabolism producing defensive phytochemicals. In particular, under appropriate conditions, OsCPS2(ent) mRNA is specifically induced in leaves prior to production of the corresponding phytoalexins. Thus, transcriptional control of OsCPS2(ent) seems to be an important means of regulating defensive phytochemical biosynthesis. Finally, OsCPS1(ent) is significantly more similar to the likewise GA-specific gene An1/ZmCPS1(ent) in maize (Zea mays) than its class II terpene synthase paralogs involved in rice secondary metabolism. Hence, we speculate that this cross-species conservation by biosynthetic process reflects derivation of related secondary metabolism from the GA primary biosynthetic pathway prior to the early divergence between the separate lineages within the cereal/grass family (Poaceae) resulting in modern rice and maize