CHEMISTRY OF NATURAL COMPOUNDS AND BIOORGANIC CHEMISTRY - RADIATION-INDUCED INACTIVATION OF ANGIOTENSIN-CONVERTING ENZYME IN AQUEOUS-SOLUTIONS .1. THE EFFECT OF IRRADIATION CONDITIONS

Radiation-induced inactivation of angiotensin-converting enzyme (ACE) was studied. The relationship of this process to damage to aromatic am ino acid residues (tyrosine and tryptophan) was demonstrated by the me thod of second derivatives of UV spectra. In some cases, the dependenc e of inactivation on dose had an induction period. The comparison of t he radiation-induced inactivation parameters of ACE, serine proteinase s, and horseradish peroxidase points to a significant stabilizing effe ct of carbohydrate residues in glycoproteins (''autoprotective mechani sm''). At pH 7.5, conformational changes occur in ACE. Low accessibili ty of the active center of this enzyme was suggested.