The effect of heat upon the activating efficiency of enterokinase.

THE effect of heat upon the properties of enterokinase has not been studied in very great detail, and the work that has been done is not of a quantitative nature. Mellanby and Woolley [1913] stated that enterokinase is destroyed in 5 mins. at 650, and is immediately inactivated in the presence of free acid. In more recent work Waldschmidt-Leitz [1924, 1925] has shown that enterokinase solutions are inactivated when heated above 500 and that they are most stable about the neutrality point. The work described in this paper deals with a quantitative investigation of the effect of heat upon enterokinase. This has been effected in principle by maintaining an enterokinase solution at a temperature of 550, removing samples at various time intervals, and then measuring the enterokinase content of a definite volume of each sample. The procedure involves two consecutive stages. (1) Addition of a definite volume of the solution to a constant volume of buffered trypsin solution, leaving the mixed solutions at 300 for 30 mins.1, when formation of the compound trypsin-kinase takes place. (2) Addition of caseinogen and buffer solution to the trypsin-kinase at the end of the above period, and then measurement of the amount of hydrolysis of the caseinogen produced in 20 mins., reckoned from the time of addition of caseinogen to the trypsin-kinas6. Before carrying out the above steps however it is necessary to define an arbitrary enterokinase unit.