C-S lyase (CSL) enzymes are responsible for the generation of toxicity via the cleavage of cysteine conjugates to generate reactive thiol species. In order to explore and characterise CSL activity in mammalian organs, cysteine conjugate CSL enzymes were isolated from bovine pulmonary, hepatic and renal tissues. Bovine tissue”, obtained from the abbatoir, affords a readily available source of viable CSL enzymes, without the necessity of sacrificing large numbers of laboratory animals simply to provide tissue. We have demonstrated that significant CSL activity exists in bovine tissues, and that the level of this activity is comparable with that found in human tissues. These enzymes provide an explanation for the previously reported episodes of bovine toxicity, and may provide a reasonable model for other mammalian CSL enzymes.