Rate of Liberation of Tryptophane from Proteins by Enzymes.

Abstract

Casein, edestin, Witte peptone and squash seed globulin were subjected to trypsin hydrolysis. At different intervals of time a portion of the respective hydrolysates was taken and tryptophane determined by the indirect Vanillin-HCl reaction. 1 At the end of one hour three-fourths of the total available tryptophane in casein was liberated, a little less than one-half was liberated from edestin and two-fifths from squash seed globulin. Witte peptone had one-third of the total tryptophane available before incubation with trypsin and at the end of the first hour two-thirds was available. Equilibrium was established in the case of Witte peptone in 24 hours, casein in 72-96 hours, edestin and squash seed globulin in 120 hours. The latter 3 proteins were subjected to the action of pepsin, trypsin and erepsin in the order given and aliquot portions were taken and analyzed for amino nitrogen and for tryptophane. At the end of the pepsin period of 96 hours there was an average of 17% amino nitrogen but no tryptophane liberated. During the trypsin period the liberation of tryptophane and the establishment of equilibrium was the same as in the experiment with trypsin alone without any pepsin action. Erepsin action for 48 hours showed an additional liberation of 15-18% of amino nitrogen but no change in the tryptophane concentration. Thus, trypsin or a trypsin type of enzymes alone are involved in the liberation of tryptophane from the proteins studied.

The effects of sodium and chloride ions on the precipitation of tryptophane by mercuric sulfate were studied. A 0.3% concentration of chloride ion interferes with and a 0.77%'lntirely prevents the precipitation of tryptophane under the conditions as given in the indirect Vanillin-HC1 reaction.