Bacterial keratinase: prospects for prion degradation.

Infective prion protein is the agent responsible for prion diseases in human and animals. The health, environmental, and cost implications of its occurrence is enormous. The current methods of chemical and heat treatments for prion inactivation is limited by considerations of environmental acceptability, application compatibility and cost, making effective enzymatic inactivation option highly attractive. A Gram-positive bacterium has been isolated which show significant proteolytic activity on casein-agar plate and keratinolytic activity on keratin azure. Optimum keratinase activity (14 U/ml) was expressed by the crude extract of a 24h culture under optimized conditions (pH 10, 37°C and 0.8% (w/v) substrate concentration). Purified supernatant yielded active fraction with purification factor of 108.7 and specific activity of 2,000 U/mg. SDS-PAGE showed a homogenous band on gel and molecular weight was determined by Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry (MALDI MS), as 27.9 kDa. The optimum pH and temperature for this enzyme were determined as 8.5 and 50°C respectively, and showed considerable stability for up to two months when stored at 4°C as free keratinase. Recalcitrant melanized feather was degraded within 48h suggesting strong prospects for this bacterial keratinase in prion degradation since keratin and prion protein are structurally similar.