Malaria is a global health problem that threatens 300-500 million people and kills more than one million people annually. Disease control is hampered by the occurrence of multi-drug-resistant strains of the malaria parasite Plasmodium falciparum. Synthetic antimalarial drugs and malarial vaccines are currently being developed, but their efficacy against malaria awaits rigorous clinical testing. Artemisinin, a sesquiterpene lactone endoperoxide extracted from Artemisia annua L (family Asteraceae; commonly known as sweet wormwood), is highly effective against multi-drug-resistant Plasmodium spp., but is in short supply and unaffordable to most malaria sufferers. Although total synthesis of artemisinin is difficult and costly, the semi-synthesis of artemisinin or any derivative from microbially sourced artemisinic acid, its immediate precursor, could be a cost-effective, environmentally friendly, high-quality and reliable source of artemisinin. Here we report the engineering of Saccharomyces cerevisiae to produce high titres (up to 100 mg l(-1)) of artemisinic acid using an engineered mevalonate pathway, amorphadiene synthase, and a novel cytochrome P450 monooxygenase (CYP71AV1) from A. annua that performs a three-step oxidation of amorpha-4,11-diene to artemisinic acid. The synthesized artemisinic acid is transported out and retained on the outside of the engineered yeast, meaning that a simple and inexpensive purification process can be used to obtain the desired product. Although the engineered yeast is already capable of producing artemisinic acid at a significantly higher specific productivity than A. annua, yield optimization and industrial scale-up will be required to raise artemisinic acid production to a level high enough to reduce artemisinin combination therapies to significantly below their current prices.

In 2010 there were more than 200 million cases of malaria, and at least 655,000 deaths 1 . The World Health Organization has recommended artemisinin-based combination therapies (ACTs) for the treatment of uncomplicated malaria caused by the parasite Plasmodium falciparum. Artemisinin is a sesquiterpene endoperoxide with potent antimalarial properties, produced by the plant Artemisia annua. However, the supply of plant-derived artemisinin is unstable, resulting in shortages and price fluctuations, complicating production planning by ACT manufacturers 2 . A stable source of affordable artemisinin is required. Here we use synthetic biology to develop strains of Saccharomyces cerevisiae (baker's yeast) for high-yielding biological production of artemisinic acid, a precursor of artemisinin. Previous attempts to produce commercially relevant concentrations of artemisinic acid were unsuccessful, allowing production of only 1.6 grams per litre of artemisinic acid 3 . Here we demonstrate the complete biosynthetic pathway, including the discovery of a plant dehydrogenase and a second cytochrome that provide an efficient biosynthetic route to artemisinic acid, with fermentation titres of 25 grams per litre of artemisinic acid. Furthermore, we have developed a practical, efficient and scalable chemical process for the conversion of artemisinic acid to artemisinin using a chemical source of singlet oxygen, thus avoiding the need for specialized photochemical equipment. The strains and processes described here form the basis of a viable industrial process for the production of semi-synthetic artemisinin to stabilize the supply of artemisinin for derivatization into active pharmaceutical ingredients (for example, artesunate) for incorporation into ACTs. Because all intellectual property rights have been provided free of charge, this technology has the potential to increase provision of first-line antimalarial treatments to the developing world at a reduced average annual price.Before the discovery of the enzymes that complete the biosynthetic pathway of artemisinin production (see Supplementary Fig. 1 for a complete overview), several improvements were made to the original amorphadiene-producing strain Y337 (ref. 3). We replaced the MET3 promoter with the copper-regulated CTR3 promoter (Fig. 1a), enabling restriction of ERG9 expression (ERG9 encodes squalene synthase, which catalyses the competing reaction of joining two farnesyl diphosphate moieties to form squalene) by addition of the inexpensive repressor CuSO 4 to the medium rather than the more expensive methionine 4-6 . Strains Y1516 (P CTR3 -ERG9) and Y337 (P MET3 -ERG9) (Supplementary Table 1) both produced similar amounts of amorphadiene ( Supplementary Fig. 2), demonstrating the equivalence of the MET3 and CTR3 promoters for repression of ERG9 expression. We compared the production of amorphadiene from Y337 with the production of artemisinic acid from Y285, a variant of Y337 that also expressed the amorphadiene oxidase CYP71AV1 (a cytochrome P450) and A. annua CPR1 (...

Production of fine heterologus pathways in microbial hosts is frequently hindered by insufficient knowledge of the native metabolic pathway and its cognate enzymes; often the pathway is unresolved and enzymes lack detailed characterization. An alternative paradigm to using native pathways is de novo pathway design using well-characterized, substrate-promiscuous enzymes. We demonstrate this concept using P450 BM3 from Bacillus megaterium. Using a computer model, we illustrate how key P450 BM3 activ site mutations enable binding of non-native substrate amorphadiene, incorporating these mutations into P450 BM3 enabled the selective oxidation of amorphadiene arteminsinic-11s,12-epoxide, at titers of 250 mg L "1 in E. coli. We also demonstrate high-yeilding, selective transformations to dihydroartemisinic acid, the immediate precursor to the high value anti-malarial drug artemisinin.

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We are exposed to a growing number of chemicals in our environment, most of which have not been characterized in terms of their toxicological potential or mechanisms. Here, we employ a chemoproteomic platform to map the cysteine reactivity of environmental chemicals using reactivity-based probes to mine for hyper-reactive hotspots across the proteome. We show that environmental contaminants such as monomethylarsonous acid and widely used pesticides such as chlorothalonil and chloropicrin possess common reactivity with a distinct set of proteins. Many of these proteins are involved in key metabolic processes, suggesting that these targets may be particularly sensitive to environmental electrophiles. We show that the widely used fungicide chlorothalonil specifically inhibits several metabolic enzymes involved in fatty acid metabolism and energetics, leading to dysregulated lipid metabolism in mice. Our results underscore the utility of using reactivity-based chemoproteomic platforms to uncover novel mechanistic insights into the toxicity of environmental chemicals.

The structure-activity relationships of organophosphorus (OP) and organosulfur compounds were examined in vitro and in vivo as inhibitors of mouse brain monoacylglycerol lipase (MAGL) hydrolysis of 2-arachidonoylglycerol (2-AG) and agonist binding at the CB1 receptor. Several compounds showed exceptional potency towards MAGL activity with IC 50 values of 0.1-10 nM in vitro and high inihibition at 10 mg/kg intraperitoneally in mice. We find for the first time that MAGL activity is a major in vivo determinant of 2-AG and arachidonic acid levels not only in brain but also in spleen, lung and liver. Apparent direct OP inhibition of CB1 agonist binding may be due instead to metabolic stabilization of 2-AG in brain membranes as the actual inhibitor. Keywords Monoacylglycerol lipase inhibitors; 2-Arachidonoylglycerol; Arachidonic acidThe endocannabinoids (EC) 2-arachidonoylglycerol (2-AG) and anandamide (AEA) regulate a diverse array of neurological and metabolic functions and are altered by neuropathic pain, anxiety, neurodegeneration, obesity and cardiovascular disorders. 1 2-AG is a full agonist towards the cannabinoid receptor type 1 (CB1) and its signaling is terminated primarily by monoacylglycerol lipase (MAGL). AEA levels are regulated by fatty acid amide hydrolase (FAAH). 2-4 Augmentation of EC signaling by blockade of 2-AG or AEA degradation (Scheme 1) is proposed as a therapeutic strategy. However, characterization of MAGL or 2-AG in brain and peripheral tissues is hindered by the paucity of systemic MAGL inhibitors and lack of a MAGL knockout mouse. Discovery of potent MAGL inhibitors is therefore essential in understanding the biochemical, physiological and therapeutic roles of this enzyme.Structural manipulation of organophosphorus (OP) and organosulfur (OS) compounds (Scheme 2) can potentially confer potency and selectivity for MAGL and FAAH compared to * Corresponding author. Tel.: +1 510 642 5424; fax: +1 510 642 6497. E-mail address: ectl@nature.berkeley.edu (J.E. Casida). Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. This study reports structure-activity relationships of OPs and OSs with MAGL, FAAH and CB1 and uses these tools to consider three interrelationships of the EC system components. The first is the in vitro potency for inhibiting MAGL, FAAH and CB1 agonist binding as a predictor of in vivo behavioral effects and pharmacological profile. The second is the variation among tissues in their MAGL activity and differential regulation of 2-AG and AA levels. Finally we consider the possibility that OP displacement of CB1 agonist binding is due to 2...

Acetanilide herbicides are among the most widely used pesticides in the United States, but their toxicological potential and mechanisms remain poorly understood. Here, we have used chemoproteomic platforms to map proteome-wide cysteine reactivity of acetochlor (AC), the most widely used acetanilide herbicide, in vivo in mice. We show that AC directly reacts with >20 protein targets in vivo in mouse liver, including the catalytic cysteines of several thiolase enzymes involved in mitochondrial and peroxisomal fatty acid oxidation. We show that the fatty acids that are not oxidized, due to impaired fatty acid oxidation, are instead diverted into other lipid pathways, resulting in heightened free fatty acids, triglycerides, cholesteryl esters, and other lipid species in the liver. Our findings show the utility of chemoproteomic approaches for identifying novel mechanisms of toxicity associated with environmental chemicals like acetanilide herbicides.

Lipases sensitive to organophosphorus (OP) inhibitors play critical roles in cell regulation, nutrition, and disease, but little is known on the toxicological aspects in mammals. To help fill this gap, six lipases or lipase-like proteins are assayed for OP sensitivity in vitro under standard conditions (25 degrees C, 15 min incubation). Postheparin serum lipase, lipoprotein lipase (LPL) (two sources), pancreatic lipase, monoacylglycerol (MAG) lipase, cholesterol esterase, and KIAA1363 are considered with 32 OP pesticides and related compounds. Postheparin lipolytic activity in rat serum is inhibited by 14 OPs, including chlorpyrifos oxon (IC50 50-97 nM). LPL (bovine milk and Pseudomonas) generally is less inhibited by the insecticides or activated oxons, but the milk enzyme is very sensitive to six fluorophosphonates and benzodioxaphosphorin oxides (IC50 7-20 nM). Porcine pancreatic lipase is very sensitive to dioctyl 4-nitrophenyl phosphate (IC50 8 nM), MAG lipase of mouse brain to O-4-nitrophenyl methyldodecylphosphinate (IC50 0.6 nM), and cholesterol esterase (bovine pancreas) to all of the classes of OPs tested (IC50< 10 nM for 17 compounds). KIAA1363 is sensitive to numerous OPs, including two O-4-nitrophenyl compounds (IC50 3-4 nM). In an overview, inhibition of 28 serine hydrolases (including lipases) by eight OPs (chlorpyrifos oxon, diazoxon, paraoxon, dichlorvos, and four nonpesticides) showed that brain acetylcholinesterase is usually less sensitive than butyrylcholinesterase, liver esterase, cholesterol esterase, and KIAA1363. In general, each lipase (like each serine hydrolase) has a different spectrum of OP sensitivity, and individual OPs have unique ranking of potency for inhibition of serine hydrolases.