Biocatalytic Production of Aldehydes: Exploring the Potential of Lathyrus cicera Amine Oxidase

Aldehydes are a class of carbonyl compounds widely used as intermediates in the pharmaceutical, cosmetic and food industries. To date, there are few fully enzymatic methods for synthesizing these highly reactive chemicals. In the present work, we explore the biocatalytic potential of an amino oxidase extracted from the etiolated shoots of Lathyrus cicera for the synthesis of value-added aldehydes, starting from the corresponding primary amines. In this frame, we have developed a completely chromatography-free purification protocol based on crossflow ultrafiltration, which makes the production of this enzyme easily scalable. Furthermore, we determined the kinetic parameters of the amine oxidase toward 20 differently substituted aliphatic and aromatic primary amines, and we developed a biocatalytic process for their conversion into the corresponding aldehydes. The reaction occurs in aqueous media at neutral pH in the presence of catalase, which removes the hydrogen peroxide produced during the reaction itself, contributing to the recycling of oxygen. A high conversion (>95%) was achieved within 3 h for all the tested compounds.

Refinement of the Peroxidase Peptide Reactivity Assay and Prediction Model for Assessing Skin Sensitization Potential

A peptide reactivity assay with an activation component was developed for use in screening chemicals for skin sensitization potential. A horseradish peroxidase-hydrogen peroxide (HRP/P) oxidation system was incorporated into the assay for characterizing reactivity of hapten and pre-/prohapten sensitizers. The assay, named the Peroxidase Peptide Reactivity Assay (PPRA) had a predictive accuracy of 83% (relative to the local lymph node assay) with the original protocol and prediction model. However, apparent false positives attributed to cysteine depletion at relatively high chemical concentrations and, for some chemicals expected to react with the −NH2 group of lysine, little to no depletion of the lysine peptide were observed. To improve the PPRA, cysteine peptide reactions with and without HRP/P were modified by increasing the number of test concentrations and refining their range. In addition, removal of DL-dithiothreitol from the reaction without HRP/P increased cysteine depletion and improved detection of reactive aldehydes and thiazolines without compromising the assay’s ability to detect prohaptens. Modification of the lysine reaction mixture by changing the buffer from 0.1 M ammonium acetate buffer (pH 10.2) to 0.1 M phosphate buffer (pH 7.4) and increasing the level of organic solvent from 1% to 25% resulted in increased lysine depletion for known lysine reactive chemicals. Refinement of the prediction model improved the sensitivity, specificity, and accuracy for hazard identification. These changes resulted in significant improvement of the PPRA making it is a reliable method for predicting the skin sensitization potential of all chemicals, including pre-/prohaptens and directly reactive haptens.

Airborne occupational exposures and inflammatory biomarkers in the Lifelines cohort study

IntroductionInflammatory biomarkers are associated with negative health outcomes. In this study, we investigated the associations between airborne occupational exposures and levels and changes in inflammatory biomarkers.MethodsWe included 79 604 adults at baseline from the Lifelines cohort of which 48 403 (60.8%) subjects were followed for a median of 4.5 years. Airborne occupational exposures at the current or last-held job at baseline were estimated with the occupational asthma-specific job-exposure matrix. Both in cross-sectional and longitudinal analyses, we used linear regression models (adjusted for age, sex, education, monthly income, body mass index, smoking, pack-years, asthma and anti-inflammatory medication) to investigate the associations between airborne occupational exposures (allergens, reactive chemicals, pesticides and micro-organisms) and inflammatory biomarkers (C reactive protein (CRP), eosinophils and neutrophils).ResultsIn the cross-sectional analyses, exposure to allergens, reactive chemicals and micro-organisms was associated with a lower (Log) CRP level (B(95% CI)=−0.05 (−0.08 to −0.02),–0.05(−0.08 to −0.02) and −0.09(−0.16 to −0.02), respectively). Likewise, exposure to allergens, reactive chemicals, pesticides and micro-organisms was associated with a lower (log) neutrophils count (−0.01 (−0.02 to −0.01), −0.01 (−0.02 to −0.01),–0.02 (−0.04 to −0.01) and −0.02(−0.03 to −0.01), respectively). No association between airborne occupational exposures and eosinophils count was found. In the longitudinal analyses, no association between airborne occupational exposures and changes in inflammatory biomarkers was found.ConclusionsAt baseline, airborne occupational exposures are inversely associated with inflammation; no effect of occupational exposures on inflammation was found at follow-up. In the future studies, details of occupational exposures, such as duration of exposures and cumulative exposures, need to be included to investigate the airborne occupational exposures and inflammatory biomarkers.

Parental occupational exposure pre- and post-conception and development of asthma in offspring

Background While direct effects of occupational exposures on an individual’s respiratory health are evident, a new paradigm is emerging on the possible effects of pre-conception occupational exposure on respiratory health in offspring. We aimed to study the association between parental occupational exposure starting before conception and asthma in their offspring (at 0–15 years of age). Methods We studied 3985 offspring participating in the Respiratory Health in Northern Europe, Spain and Australia (RHINESSA) generation study. Their mothers or fathers (n = 2931) previously participated in the European Community Respiratory Health Survey (ECRHS). Information was obtained from questionnaires on parental job history pre- and post-conception which was linked to an asthma-specific job-exposure matrix (JEM). We assessed the association between parental occupational exposure and offspring asthma, applying logistic regression models, clustered by family and adjusted for study centre, offspring sex, parental characteristics (age, asthma onset, place of upbringing, smoking) and grandparents’ level of education. Results Parental occupational exposure to microorganisms, pesticides, allergens or reactive chemicals pre-conception or both pre- and post-conception was not related to offspring asthma; in general, subgroup analyses confirmed this result. However, maternal exposure both pre- and post-conception to allergens and reactive chemicals was associated with increased odds for early-onset asthma in offspring (0–3 years of age); odds ratio 1.70 (95% CI: 1.02–2.84) and 1.65 (95% CI: 0.98–2.77), respectively. Conclusions This study did not find evidence that parental occupational exposure, defined by an asthma JEM before conception only or during pre- and post-conception vs non-exposed, was associated with offspring asthma.

Extracellularly oxidative activation and inactivation of matured prodrug for cryptic self-resistance in naphthyridinomycin biosynthesis

Understanding how antibiotic-producing bacteria deal with highly reactive chemicals will ultimately guide therapeutic strategies to combat the increasing clinical resistance crisis. Here, we uncovered a distinctive self-defense strategy featured by a secreted oxidoreductase NapU to perform extracellularly oxidative activation and conditionally overoxidative inactivation of a matured prodrug in naphthyridinomycin (NDM) biosynthesis from Streptomyces lusitanus NRRL 8034. It was suggested that formation of NDM first involves a nonribosomal peptide synthetase assembly line to generate a prodrug. After exclusion and prodrug maturation, we identified a pharmacophore-inactivated intermediate, which required reactivation by NapU via oxidative C-H bond functionalization extracellularly to afford NDM. Beyond that, NapU could further oxidatively inactivate the NDM pharmacophore to avoid self-cytotoxicity if they coexist longer than necessary. This discovery represents an amalgamation of sophisticatedly temporal and spatial shielding mode conferring self-resistance in antibiotic biosynthesis from Gram-positive bacteria.

Direct electrochemical generation of organic carbonates by dehydrogenative coupling

Organic carbonates are an important source for polycarbonate synthesis. However, their synthesis generally requires phosgene, sophisticated catalysts, harsh reaction conditions, or other highly reactive chemicals. We present the first direct electrochemical generation of mesityl methyl carbonate by C–H activation. Although this reaction pathway is still challenging concerning scope and efficiency, it outlines a new strategy for carbonate generation.