Some properties of the cathepsin from the mucosa of rat colon.

In our previous work we purified and characterized the cathepsins from the small intestine of pig and rat 2. Colon is a part of digestive tract which morphologically and functionaly differs from the small intestine. For this reason we isolated and characterized the cathepsin from the mucosa of rat colon to see whether there are some differences in properties of both enzymes. Wistar albino rats, 4 — 6 months old were used for the experiments. The animals were anesthetized, the obdomen was opened and large intestine was isolated from caecum to the end of colon descendens. The gut was opened and washed thoroughly with ice-cold saline solution. The mucosa was scrapped off and homogenized in water with Potter-Elvehjem teflon pestle homogenizer. After acidification to PH 4.0 homogenate was centrifuged. In the clear supernatant the proteins were precipitated with ammonium sulphate. Precipitate was dissolved in 0.1 M NaCl and the excess of the ammonium sulphate was removed by dialysis. The final purification of the enzyme was performed by gel filtration on Sephadex G-75, following by rechromatography of active fraction on Sephadex G-75. The determination of some enzyme characteristics was performed as previously described 1. After incubation of the cathepsin for 2 hours at different PH it was found that the enzyme is most stable at PH 5; at PH optimum its stability is 60 per cent. Optimal temperature for hemoglobin hydrolysis was 50 °C. It was found that the cathepsin was thermally unstable. After heating for 30 minutes at 60 °C the