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

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

Age-Related Changes of Plasma Bile Acid Concentrations in Healthy Adults—Results from the Cross-Sectional KarMeN Study

Bile acids (BA) play an important role in lipid metabolism. They facilitate intestinal lipid absorption, and BA synthesis is the main catabolic pathway for cholesterol. The objective of this study was to investigate associations of age, sex, diet (fat intake) and parameters of lipid metabolism (triglycerides, LDL, HDL, body fat content) with fasting plasma BA concentration of healthy individuals. Fasting plasma samples from a cross-sectional study were used to determine the concentrations of 14 BA using an LC-MS stable isotope dilution assay. Triglycerides, LDL and HDL were analyzed by standard clinical chemistry methods and body fat content was measured with a DXA instrument. The dietary fat intake of the 24 h period prior to the sampling was assessed on the basis of a 24 h recall. Subsequent statistical data processing was done by means of a median regression model. Results revealed large inter-individual variations. Overall, higher median plasma concentrations of BA were observed in men than in women. Quantile regression showed significant interactions of selected BA with age and sex, affecting primarily chenodeoxycholic acid and its conjugates. No associations were found for LDL and the amount of fat intake (based on the percentage of energy intake from dietary fat as well as total fat intake). Additional associations regarding body fat content, HDL and triglycerides were found for some secondary BA plasma concentrations. We conclude that age and sex are associated with the fasting plasma concentrations. Those associations are significant and need to be considered in studies investigating the role of BA in the human metabolism