1.Production of FAME biodiesel in E. coli by direct methylation with an insect enzyme.
Sherkhanov S1, Korman TP1, Clarke SG1, Bowie JU1. Sci Rep. 2016 Apr 7;6:24239. doi: 10.1038/srep24239.
Most biodiesel currently in use consists of fatty acid methyl esters (FAMEs) produced by transesterification of plant oils with methanol. To reduce competition with food supplies, it would be desirable to directly produce biodiesel in microorganisms. To date, the most effective pathway for the production of biodiesel in bacteria yields fatty acid ethyl esters (FAEEs) at up to ~1.5 g/L. A much simpler route to biodiesel produces FAMEs by direct S-adenosyl-L-methionine (SAM) dependent methylation of free fatty acids, but FAME production by this route has been limited to only ~16 mg/L. Here we employ an alternative, broad spectrum methyltransferase, Drosophila melanogaster Juvenile Hormone Acid O-Methyltransferase (DmJHAMT). By introducing DmJHAMT in E. coli engineered to produce medium chain fatty acids and overproduce SAM, we obtain medium chain FAMEs at titers of 0.56 g/L, a 35-fold increase over titers previously achieved. Although considerable improvements will be needed for viable bacterial production of FAMEs and FAEEs for biofuels, it may be easier to optimize and transport the FAME production pathway to other microorganisms because it involves fewer enzymes.
2.Application of AlkBGT and AlkL from Pseudomonas putida GPo1 for selective alkyl ester ω-oxyfunctionalization in Escherichia coli.
van Nuland YM1, Eggink G2, Weusthuis RA3. Appl Environ Microbiol. 2016 Apr 15. pii: AEM.00822-16. [Epub ahead of print]
The enzyme system AlkBGT fromPseudomonas putidaGPo1 can efficiently ω-functionalize fatty acid methyl esters. Outer membrane protein AlkL boosts this ω-functionalization. In this study it is shown that whole-cells ofE. coliexpressing the AlkBGT system can also ω-oxidize ethyl nonanoate (NAEE). Co-expression of AlkBGT and AlkL resulted in 1.7-fold higher ω-oxidation activity on NAEE. With this strain, initial activity on NAEE was 70 U/gcdw, 67% of the initial activity on methyl nonanoate. In time-lapse conversions with 5 mM NAEE the main product was 9-hydroxy NAEE (3.6 mM), but also 9-oxo NAEE (0.1 mM) and 9-carboxy NAEE (0.6 mM) were formed. AlkBGT also ω-oxidized ethyl, propyl and butyl esters of fatty acids ranging from C6 to C10. Increasing the length of the alkyl chain improved the ω-oxidation activity of AlkBGT on esters of C6 and C7 fatty acids. From these esters, application of butyl hexanoate resulted in the highest ω-oxidation activity of 82 U/gcdw Co-expression of AlkL only had a positive effect on ω-functionalization of substrates with a total length of C11 or longer.
3.Membrane-permeable Mn(III) complexes for molecular MRI of intracellular targets.
Barandov A, Bartelle BB, Gonzalez BA, White WL, Lippard SJ, Jasanoff A. J Am Chem Soc. 2016 Apr 18. [Epub ahead of print]
Intracellular compartments make up roughly two thirds of the body, but delivery of molecular imaging probes to these spaces can be challenging. This situation is particularly true for probes designed for detection by magnetic resonance imaging (MRI), a high resolution but relatively insensitive modality. Most MRI contrast agents are polar and membrane impermeant, making it difficult to deliver them in sufficient quantities for measurement of intracellular analytes. Here we address this problem by introducing a new class of planar tetradentate Mn(III) chelates assembled from a 1,2-phenylenediamido (PDA) backbone. Mn(III)-PDA complexes display T1 relaxivity comparable to that of Gd(III)-based contrast agents and undergo spontaneous cytosolic localization via defined mechanisms. Probe variants incorporating enzyme-cleavable acetomethoxy ester groups are processed by intracellular esterases and accumulate in cells. Probes modified with ethyl esters preferentially label genetically modified cells that express a substrate-selective esterase.
4.Structure-activity relationship studies of new rifamycins containing l-amino acid esters as inhibitors of bacterial RNA polymerases.
Czerwonka D1, Domagalska J1, Pyta K1, Kubicka MM2, Pecyna P2, Gajecka M3, Przybylski P4. Eur J Med Chem. 2016 Mar 24;116:216-221. doi: 10.1016/j.ejmech.2016.03.061. [Epub ahead of print]
New rifamycins (1-12) combined with different l-amino acids, containing methyl, ethyl, tert-butyl and benzyl groups at the ester part, via amine linkage, were synthesized and their structures in solution were determined by spectroscopic FT-IR and 1D and 2D NMR methods as well as visualized by DFT calculations. Two types of rifamycin structures were detected in solution: a zwitterionic one with the transferred proton from O(8)H phenol to secondary N(38) atom and a pseudocyclic structure stabilized via formation of intramolecular H-bond within the protonated basic C(3)-substituent. The presence of these rifamycins' structures influenced physico-chemical (logP, solubility) parameters and antibacterial properties. The bulkiness at the ester substituent of new rifamycins containing aromatic l-amino acids was found to be an important factor, besides the solubility, to achieve relatively high antibacterial activity against reference S. epidermidis and reference S.
