The Estimation of Pepsin, Trypsin, Papain, and Cathepsin With Hemoglobin

In the hemoglobin method for the estimation of proteinase, denatured hemoglobin is digested under standard conditions, the undigested hemoglobin is precipitated with trichloracetic acid, and the amount of unprecipitated protein split products, which is a measure of the amount of proteinase present, is estimated with the phenol reagent which gives a blue color with tyrosine and tryptophane.