Disulphide exchange reactions in the control of enzymic activity. Evidence for the participation of dimethyl disulphide in exchanges.

The causative agent in kale poisoning of cattle is the disulphide, dimethyl disulphide. Typical signs of kale poisoning are circulating dimethyl disulphide in the blood, Heinz body (deposits of methaemoglobin) formation in the erythrocytes and loss of body weight. Experiments in vitro have demonstrated that dimethyl disulphide can participate in disulphide exchange reactions which have a controlling role on proteolytic enzymes. We chose the enzyme trypsin, the active centre of which is maintained by a significant disulphide bond and the enzyme papain which is a thiol protease, to illustrate the mechanisms involved in these disulphide exchange reactions.