Scientists solve key mystery of scrapie and BSE

ONE OF the biggest mysteries in the 30-year history of research into "prion diseases", such as scrapie in sheep, BSE in cattle and CJD in humans, may finally have been solved.

A team of scientists from Cambridge University has discovered the reason every animal - including humans - makes prions even though abnormal forms of the protein can cause degenerative brain disorders. David Brown, a Cambridge biochemist, believes that prions are produced naturally in the brain and other parts of the body as a defence against the highly reactive form of oxygen, called superoxide, which is produced as a by-product of breathing air.

"All animals need oxygen and as a consequence of using oxygen they produce something called superoxide, which is basically an oxygen with an extra electron stuck on to it," Dr Brown said. "This is quite dangerous because the electron can shoot off and damage cells and proteins. Any protein that is there to make this superoxide less harmful is of benefit."

Dr Brown manufactured pure forms of the prion protein to show that it acts as a superoxide dismutase - an enzyme that can rob superoxide of its harmful electron and in doing so render it less harmful to living tissue.

The findings, to be published in the Biochemical Journal, could finally solve the problem of why animals ranging from chickens and goats to mice and humans all have prions.

Dr Brown said if the normal function of prion proteins could be understood there was a better chance of knowing how to treat the problems arising when the proteins change into their disease-causing version.