A simple and sensitive chromogen assay for the measurement of elastase-type enzyme activity in human plasma

A highly sensitive, precise and fast automatic chromogen assay has been developed for estimation of elastase-type activity in plasma using 3-carboxypropionyl-trialanine p-nitro-anilide as substrate. The assay is linear up to at least 8.7 U/l and has a detection limit of 0.003 U/l. The study demonstrates that this enzyme activity is due to one or several metalloproteinases with pH optimum at physiological pH. The plasma enzyme activity in 37 healthy persons ranged from 0.10 U/l to 0.63 U/l. The individual day to day variation was found to be about 12%. In plasma pools prepared from randomly taken samples of in- and out-patients the activity was found up to 8.7 U/l. The origin of the metalloelastase activity is discussed.