[Target proteins and mechanisms of ochratoxin toxicity. A contribution to the identification of potential ochratoxin antagonists]

Ochratoxins are mycotoxins released by moulds on grain, peanuts and vegetables. Toxicological investigations have shown that ochratoxin A displays nephrotoxic, genotoxic, teratogenic, cancerogenic and immunosuppressive effects. Increased blood levels observed in humans would seem to suggest a link to a kidney desease (Balcan Endemic Nephropaty) frequently observed in the Balkan countries. The adverse effects of ochratoxin A are mainly associated with its impact on phenylalanine-metabolizing enzymes. Based on the three-dimensional structure of phenylalanine-t-RNA-synthetase, its interactions with ochratoxins are analyzed as well as with Aspartam. In animal models, Aspartam has been shown to almost fully prevent toxic effects of ochratoxin A. The topology of the binding site of phenylalanine-t-RNA-synthetase would seem to be favorable towards a few affinity-enhancing modifications of the Aspartame molecule. A known molecular mechanism is a prerequisite for a systematic search of antagonizing substances for toxins. Based on a receptor structure, binding properties of such drugs can be identified and optimized using computer-aided drug design. Susequently, only the most potent candidate structures must be subjected to a determination of their biological activity, which can lead to a significant reduction of substances to be tested in vivo. Such experiments are particularly stressful as the animals must be intoxicated beforehand. The extent of an antagonistic impact on humans suffering from a chronical ochratoxin A intoxication must be subject of clinical studies.