In vitro studies on the indirect effects of radiation on enzymes have
been reviewed. For a better understanding an attempt has been made to
classify radiation-induced inactivation of enzymes based on structural
features of enzyme molecules. Oxygen effect on enzyme inactivation ha
s also been emphasized. Inactivation caused by reactions with water-de
rived free radicals as well as with some inorganic and organic free ra
dicals has been discussed.