46 research outputs found

    Exploring donor substrate promiscuity of a Thermostable Transketolase by directed evolution

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    Enzymes catalyzing asymmetric carboligation reactions typically show very high specificity for their nucleophilic substrate. Transketolase (TK, EC 2.2.1.1) catalyses a reversible transfer of a hydroxylated C2 fragment among phosphorylated ketoses and aldoses. [1] Native TK converts a large variety of (2R)-hydroxyaldehydes as the electrophilic acceptor substrates, but apart from its natural phosphoketose donors TK accepts only hydroxy­pyruvate (hydroxylated donor) (Figure 1). In contrast, 1-deoxy-D-xylulose-5-phosphate synthase (DXS, EC 2.2.1.7) catalyzes the specific decarboxylative transfer of the acetyl moiety from pyruvate (non-hydroxylated donor) to glyceraldehyde-3-phosphate to yield 1-deoxy-D-xylulose 5-phosphate (DXP), which constitutes the first step into the non-mevalonate biosynthesis of terpenoids (Figure 1).[2] Reactions of native TK and DXS are mutually exclusive in vivo. Please click Additional Files below to see the full abstract

    Euglycemic diabetic ketoacidosis: another masquerader!

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    Euglycemic ketoacidosis is defined by the triad of euglycemia, metabolic acidosis and ketonemia or ketonuria. In the current era of diabetic management, it is a serious concern with the usage of sodium glucose co-transporter 2 (SGLT2) inhibitors potentiated by a number of precipitating agents. Empagliflozin though a novel oral hypoglycemic agent in this category may also lead to this potential complication. Here we report a 59 year old male, type 2 diabetic who was on empagliflozin and presented with euglycemic ketoacidosis after a binge of alcohol.

    Can serum ferritin levels predict the severity of dengue early?: an observational study

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    Background: Dengue infection is a major public health threat; early recognition is crucial to improve the survival in severe dengue. Although there are various biomarkers to predict the severity of dengue, they are not routinely used in clinical practice for prognostication. We analyzed whether serum ferritin can be used to predict the severity at an earlier stage.Methods: A hospital based prospective observational study was done involving 119 dengue cases diagnosed by positive NS1 antigen or dengue specific serology (capture ELISA). Serum ferritin was measured in all at the time of diagnosis. Clinical and platelet count monitoring was done daily; classified as severe and non-severe according to 2009 WHO criteria.Results: Out of 119, 5 developed severe dengue; patients with severe dengue had significantly lower median platelet count (p<0.0001); higher ferritin levels (p=0.03) and hospital stay (p<0.0001) than non-severe group. Age had a significant negative co-relation with platelet count (r= -0.427; p<0.0001); positive correlation with ferritin levels (r=0.16; p=0.08) and hospital stay (r= 0.26; p=0.004) indicating that elderly subjects are at risk of severe disease. Serum ferritin levels negatively correlated with the platelet count (r= -0.51 p<0.001). High ferritin levels in severe cases are noted from day 4 of clinical illness.Conclusions: Elevated serum ferritin levels can be used as a potential early prognostic marker to predict the severity of dengue infection in clinical practice

    Evaluation of oral hygiene practices and awareness among dental students in Namakkal district.

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    Aim and objectives: The aim of this study was to evaluate oral hygiene practices and awareness among dental students from three dental colleges in Namakkal district. Materials and methods: A cross sectional study was conducted among dental students from three dental colleges in Namakkal district. The oral hygiene knowledge among the study group was assessed through a questionnaire, with 16 questions. Results: A total of 471 students took part in the study. 85% students used a combination of vertical and horizontal type of brushing. The use of mouthwash was only 41%. About 66% students visited a dentist only in case of oral or dental problems. 12% had bleeding on brushing, 5% had bad breath. Conclusion: Dental students themselves fall short of their expectation. Dental students need to follow proper oral hygiene practices properly in order to educate the general public

    Recent Applications of Carbon‐Nitrogen Lyases in Asymmetric Synthesis of Noncanonical Amino Acids and Heterocyclic Compounds

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    Carbon-nitrogen (C−N) lyases are enzymes that normally catalyze the cleavage of C−N bonds. Reversing this reaction towards carbon-nitrogen bond formation can be a powerful approach to prepare valuable compounds that could find applications in everyday life. This review focuses on recent (last five years) applications of native and engineered C−N lyases, either as stand-alone biocatalysts or as part of multienzymatic and chemoenzymatic cascades, in enantioselective synthesis of noncanonical amino acids and dinitrogen-fused heterocycles, which are useful tools for neurobiological research and important synthetic precursors to pharmaceuticals and food additives

    Biocatalytic Asymmetric Cyclopropanations via Enzyme‐bound Iminium Ion Intermediates

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    Cyclopropane rings are an important structural motif frequently found in many natural products and pharmaceuticals. Commonly, biocatalytic methodologies for the asymmetric synthesis of cyclopropanes rely on repurposed or artificial heme enzymes. Here, we engineered an unusual cofactor‐independent cyclopropanation enzyme based on a promiscuous tautomerase for the enantioselective synthesis of various cyclopropanes via the nucleophilic addition of diethyl 2‐chloromalonate to α,ÎČ‐unsaturated aldehydes. The engineered enzyme promotes formation of the two new carbon‐carbon bonds with excellent stereocontrol over both stereocenters, affording the desired cyclopropanes with high diastereo‐ and enantiopurity (d.r. up to 25:1; e.r. up to 99:1). Our results highlight the usefulness of promiscuous enzymes for expanding the biocatalytic repertoire for non‐natural reactions

    Means and methods for synthesizing precursors of y-aminobutyric acid (gaba) analogs

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    The invention relates to the fields of drug development and biocatalysis, more specifically to a biocatalytic route for asymmetric synthesis of precursors of y-aminobutyric acid (GABA) analogs. Provided is an isolated mutant 4-oxalocrototonate tautomerase (4-OT) enzyme comprising the following mutations (i) leucine at position 8 substituted with a tyrosine (L8Y) or a phenylalanine (L8F); (ii) methionine at position 45 substituted with a tyrosine (M45Y); and (iii) phenylalanine at position 50 substituted with an alanine (F50A), wherein the positions are numbered according to the amino acid sequence of 4-OT of Pseudomonas putida. Also provided is a method for the synthesis of a precursor for the pharmaceutically relevant enantiomer of a GABA analog, comprising (i) providing a y-nitroaldehyde using the 4-OT mutant enzyme, followed by (ii) subjecting the thus obtained y-nitroaldehyde to an enzymatic oxidation reaction catalyzed by an aldehyde dehydrogenase (EC 1.2.1.3)
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