Determination of Elastolytic Activity with 125I and 131I Labelled Elastin

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Abstract
A method is described for the preparation of iodine labelled elastin of high specific activity using 131I or 125I. The labelled elastin is used as substrate for the study of the kinetics of elastolysis with crystalline elastase. Its high sensitivity renders the method suitable for the detection and determination of low levels of elastolytic activity. This method is compared to the one using azo‐dyed elastin (“azoelastin”). Similar kinetics, with a lag period are obtained with both methods. The enzyme concentration v. s. activity curve is a straight line with both methods up to a ratio of enzyme to substrate of 1:50 at least. The advantages of this method over the others proposed is its greater sensitivity and its safe use in colored and turbid media.This method was used for the detection of elastolytic activity in a number of animal, plant and fungal enzyme preparations. High activity was associated with pepsin, papaïn and pronase. Low, but distinct activity, was present in α‐chymotrypsin and ficin preparations. A purified bacterial collagenase had an intermediary activity. Crystalline trypsin had a very low, hardly detectable activity and plasmin had no activity.

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