A new fluorescent microassay method for pepsin using succinyl-albumin.

A method was developed for fluorescent microassay of pepsin with a fluorescent reagent, fluorescamine, and a nonquenching substrate, succinyl-albumin. In this method hydrolysis of succinyl-albumin by pepsin at pH 2,0 was stopped by adding phosphate buffer, pH 6.1, and newly liberated amino groups in the reaction mixture were determined quantitatively by fluorescence after adding fluorescamine. Fluorescence increased linearly with 1.0 to 18 ng of hog pepsin. The assay was 200 times more sensitive than the modified micromethod of Anson (1939) J. Gen. Phys.22, 79–89].