*2.4.1 Precipitation by ammonium sulfate*

The serum proteins were deposed by adding 0.9 gm of ammonium sulfate (0.40%) to 4 ml of serum for patients with colon cancer, which was gradually added in ice bath with magnetic stirrer (15 minutes) until all the ammonium sulfate has been dissolved. Then the solution was placed in the centrifuge for 15 minutes and at a speed of 17,608 g to separate the precipitation from the leachate, the precipitate was dissolved with the least amount of the buffer solution (Buffer phosphate pH 7(0.001 M)). Then, the enzyme activity and protein concentration were measured.
