Cysteine protease inducing milk clotting by cleaving casein. Inhibited by HgCl(2), iodoacetamide (IAA) and, to a far lesser extent, by PMSF, Pepstatin A and EDTA. Optimum pH is 6.3. Optimum temperature is 50 degrees Celsius. On the 2D-gel the determined pI of this protein is: 3.4, its MW is: 43.67 kDa. Belongs to the intron maturase 2 family. MatK subfamily.