Oxidative stress: enzymatic detoxification of reactive carbonyl compounds in simple model organisms and man

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Cellular respiration continuously produces reactive oxygen species, which can, by lipid peroxidation, generate aggressive carbonyl compounds, contributing to ageing processes and diseases in humans.The reductive metabolism by enzymes from the short-chain dehydrogenase/reductase (SDR) superfamily effectively protects against these effects of oxidative stress. Moreover, SDR play a central role in the biotransformation of other endo- and xenobiotics.The importance of carbonyl reduction in the pathogenesis of different diseases could be strikingly demonstrated by employing model organisms. Studies on D. melanogaster show that the carbonyl reductase sniffer protects against age-dependent neurodegeneration and prolongs the lifespan of those animals. We could finally demonstrate that sniffer detoxifies a neurotoxic lipid peroxidation product, which often accumulates in tissues during degenerative diseases. This project aims at the investigation of possible functional homologs of sniffer and human carbonyl reductase 1 in the model organisms Caenorhabditis elegans, Daphnia pulex/magna and Hydra vulgaris. Bioinformatic pre-analyses show that sniffer and carbonyl reductases do occur in numerous variants in these organisms, most likely as a result of gene duplications. Particularly, Daphnia pulex, a classical test-organism, harbours numerous environment-responsive genes which predisposes it as interesting model organism in ecotoxicology but its proteins are still poorly characterised. A further approach focuses on human carbonyl reductases CBR1 and CBR3. By structure-activity comparison of the enzymes from the model organisms with both human wildtype forms and relevant CBR3>CBR1 transition mutants thereof, important structural determinants of the enzymes active sites will be identified.Based on our bioinformatics analyses, the enzymes will be cloned, recombinantly produced in both prokaryotic and eukaryotic systems and biochemically characterised. Of special interest will be their possible protective role against oxidative stress (metabolism of lipid peroxidation products or AGEs precursors). The enzymes catalytic hotspots will be determined by crystallisation and X-ray analysis. This information might give insight into the evolutionary route that led to the emergence of sniffer and carbonyl reductases and will possibly contribute to decipher their physiologic role. The results obtained with the aid of model organisms might help to elucidate basic cell-biological/biochemical mechanisms that effectively protect the human body against oxidative stress and thereby help to prevent age- and disease-associated neurodegeneration.