Ochratoxin A is a mycotoxin isolated from the Aspergillus ochraceus mold, a common fungal presence on moldy food. Ochratoxin A demonstrates nephrotoxicity and teratogenesis in animals, and shows inhibition of bacterial, yeast, and liver FARSL (phenylalanyl-tRNA synthetases) competitive with phenylalanine. As these activities are partially attenuated by phenylalanine, Ochratoxin A is suggested to produce its effects through interacting with proteins that recognize phenylalanine as a substrate, and has been demonstrated to inhibit PAH (phenylalanine hydroxylase). Derivatives of Ochratoxin A with other amino acid moieties substituted for the phenylalanine-mimic portion of the molecule demonstrate inhibition of the aminoacyl tRNA synthetases respective to those amino acids. Ochratoxin A is described to enhance lipid peroxidation and also present DNA single strand breaks, both suggesting oxidative damage as a partial mediator of Ochratoxin A cellular effects, and EPR spectroscopy with a spin trap agent identified the production of hydroxyl radicals by Ochratoxin A in the presence of NADPH. The nephrotoxic effects of Ochratoxin A are shown to be prevented by SOD (superoxide dismutase) and catalase, further indicating oxidative damage as the mediator of Ochratoxin A toxicity. Ochratoxin A is also demonstrated to increase ATP-dependent Ca2+ pump activity in renal cortex endoplasmic reticulum.