Ochratoxin A: On the Mode of Action of a Ubiquitous Mycotoxin

The production of the mycotoxin ochratoxin A (OTA) as a secondary metabolite is observed with strains of a number of comon mold species. Although ochratoxin A owes its name to the species Aspergillus ochraceus from which it was first isolated, there are also some ubiquitous species of the two orders, Aspergillus and Penicillium, being able to synthesize this compound.At the present time, more and more reports accumulate which indicate the occurrence of ochratoxin A in food and feeds in many countries, especially in Europe and North America. Thus, it seems that ochratoxin A is a mycotoxin the importance of which may have been somewhat under-estimated in former years.Several comprehensive review articles on different aspects of ochratoxin A have appeared. The first one, by Steyn (1971), emphazises the chemical features;others emphasize the analytical (Harwig, 1974;IARC, 1982), pathological (Krogh, 1977;Elling, 1977), teratogenic (Hayes, 1981) and biosynthetic aspects (Vleggaar and Steyn, 1980) of this subject. Competent reviews have also appeared by Chu (1974) and Nesheim (1976).In order to avoid too many overlaps with and repetitions of already existing reviews we attempted to concentrate on the mechanism of action of ochratoxin A. It might be fair to say that this field is only beginning to be elucidated and that to date not all findings are generally accepted as giving a consistent picture of the mode of action. We try to indicate possible, if speculative reasons for conflicting results, whenever relevant. After a brief general overview we discuss the biochemistry and molecular aspects of ochratoxin A action.