alpha,alpha '-Dihydroxyketone formation using aromatic and heteroaromatic aldehydes with evolved transketolase enzymes

Transketolase mutants have been identified that accept aromatic acceptors with good stereoselectivities, in particular benzaldehyde for which the wild type enzyme showed no activity

Inhibition of Intestinal Bile Acid Transporter Slc10a2 Improves Triglyceride Metabolism and Normalizes Elevated Plasma Glucose Levels in Mice

Interruption of the enterohepatic circulation of bile acids increases cholesterol catabolism, thereby stimulating hepatic cholesterol synthesis from acetate. We hypothesized that such treatment should lower the hepatic acetate pool which may alter triglyceride and glucose metabolism. We explored this using mice deficient of the ileal sodium-dependent BA transporter (Slc10a2) and ob/ob mice treated with a specific inhibitor of Slc10a2. Plasma TG levels were reduced in Slc10a2-deficient mice, and when challenged with a sucrose-rich diet, they displayed a reduced response in hepatic TG production as observed from the mRNA levels of several key enzymes in fatty acid synthesis. This effect was paralleled by a diminished induction of mature sterol regulatory element-binding protein 1c (Srebp1c). Unexpectedly, the SR-diet induced intestinal fibroblast growth factor (FGF) 15 mRNA and normalized bile acid synthesis in Slc10a2−/− mice. Pharmacologic inhibition of Slc10a2 in diabetic ob/ob mice reduced serum glucose, insulin and TGs, as well as hepatic mRNA levels of Srebp1c and its target genes. These responses are contrary to those reported following treatment of mice with a bile acid binding resin. Moreover, when key metabolic signal transduction pathways in the liver were investigated, those of Mek1/2 - Erk1/2 and Akt were blunted after treatment of ob/ob mice with the Slc10a2 inhibitor. It is concluded that abrogation of Slc10a2 reduces hepatic Srebp1c activity and serum TGs, and in the diabetic ob/ob model it also reduces glucose and insulin levels. Hence, targeting of Slc10a2 may be a promising strategy to treat hypertriglyceridemia and diabetes

Dual Catalysis with Two or More Biocatalysts

The remarkable activity, selectivity, and stability of many commercially available or easily prepared biocatalysts, along with their simple operative conditions and the intrinsic "greenness" of biocatalytic processes, have all contributed to a rapidly accelerating expansion of the research area dedicated to the design and development of one-pot multistep synthetic approaches involving two or more enzymes and/or microbial cells. A brief survey of the literature is presented, focusing mainly on efficient protocols that are generally applicable to a broad range of substrates and relevant to the synthesis of small, often chiral, organic molecules as synthons for the pharmaceutical and fine-chemical industries

A Multidisciplinary Approach Toward the Rapid and Preparative-Scale Biocatalytic Synthesis of Chiral Amino Alcohols: A Concise Transketolase-/omega-Transaminase-Mediated Synthesis of (2S,3S)-2-Aminopentane-1,3-diol

Chiral amino alcohols represent an important class of value-added biochemicals and pharmaceutical intermediates. Chemical routes to such compounds are generally step intensive, requiring environmentally unfriendly catalysts and solvents. This work describes a multidisciplinary approach to the rapid establishment of biocatalytic routes to chiral aminodiols taking the original synthesis of (2S,3S)-2-aminopentane-1,3-diol as a specific example. An engineered variant of Escherichi coli transketolase (D469T) was used for the initial asymmetric ynthesis of (3S)-1,3-dihydroxypentan-2-one from the achiral substrates propanal and hydroxypyruvate. A bioinformatics led strategy was then used to identify and clone an omega-transaminase from Chromobacterium violaceum (DSM30191.) capable of converting the product of the transketolase-catalysed step to the required (2S,3S)-2-aminopentane-1,3-diol using isopropylamine as an inexpensive amine donor. Experiments; to characterize, optimize and model the kinetics of each reaction step were performed at the 1 mL scale using previously established automated microwell processing techniques. The microwell results, provided excellent predictions of the reaction kinetics when the. bioconversions were subsequently scaled up to preparative scales in batch stirred-tank reactors. The microwell methods thus provide process chemists and engineers with a valuable tool for the rapid and early evaluation of potential synthetic strategies. Overall, this work describes a concise and efficient biocatalytic route to chiral amino alcohols and illustrates an integrated multidisciplinary approach to bioconversion process design and scale-up