Papain hemoglobin

Myoglobin, hemoglobin Thermolysin domain 2 T4 phage lysozyme domain 2 Papain domain 1... 

Papain is readily inactivated by PAN (at 115 ppm for 40 min), provided that it is in the sulfhydryl form. The reaction of sulfhydryl groups of hemoglobin with PAN is very similar to the reaction with p-mercuricbenzoate there is more reaction at a pH of 4.5 than at a pH of 7. However, there is one striking difference between PAN and classic compounds that react with sulfhydryl groups egg albumen is resistant to reaction with PAN. Thus, enzymes that have no free sulfhydryl groups should be quite resistant to PAN. This is the case with pancreatic ribonuclease the native enzyme was not affected by a 300-fold molar excess of PAN. 

Anson, M.L. 1938. The estimation of pepsin, trypsin, papain and cathepsin with hemoglobin. J. Gen. Physiol. 22 79-89. 

Fig. 5. The hydrolysis of several peptides from a- and jS-chains of human hemoglobin by papain. Hydrolyses were performed at for 15-18 hr at pH 5.5,...

In 1937, Balls et al. [4] purified one of the proteolytic fractions and called their crystalline enzyme papain. This was an unfortunate choice, since the name papain is also used for the crude papaya latex containing multiple enzymes. In 1939, Lineweaver and Balls published a refinement of the isolation method, and they also reported the presence in the papaya latex of another proteinase with a higher ratio of milk-clotting to hemoglobin-digesting activity than papain [5], In 1941 Jansen and Balls presented a description of a second proteolytic enzyme [6]... 

Fig. 15.37. The effect of a proteinase preparation on resistance to extension (in extensogram units) of a wheat flour dough (according to Sproessler, 1980). Proteinase preparation 1 fungal, 2 papain, and 3 bacterial. Unb proteinase activity units determined with hemoglobin as a substrate...

The assay of papain against proteins can be performed by the method of Anson (5) as modified by Kunitz (100) with urea-denatured hemoglobin as substrate. The reactions are carried out at 30 in the presence of 0.005 M cysteine and 0.001 M Versene at pH 7 to 8.5. Aliquots of the reaction mixture are removed at appropriate intervals, treated with 6% trichloroacetic acid and filtered. The filtrates are examined in a spectrophotometer at 280 mu. Appropriate controls should be run. 

Hennessey and Johnson [81H1] use CD data of 15 proteins and one helical polypeptide as their reference proteins a-chymotrypsin, cytochrome c, elastase, flavodoxin, glyceraldehyde-3-phosphate dehydrogenase, hemoglobin, lactate dehydrogenase, lysozyme, myoglobin, papain, prealbumin, ribonuclease A, subtilisin BPN, subtilisin novo, triosephosphate isomerase and (Glu)n (helical). More recently, Toumadje et al. [92T4] still use CD data of 15 proteins and one polypeptide, but have replaced lysozyme by T4 lysozyme and subtilisin BPN by EcoRI. 

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