Under certain conditions, CA I HIR-1 (86 Asp leads to Gly) was inactivated in Gnd . HCl more rapidly than normal CA I. 2. After denaturation in 5.0 M Gnd . HCl, CA I HIR-1 was reactivated more slowly than normal CA I. 3. CA I HIR-1 was precipitated by purified anti-CA I antibodies, under certain conditions, more rapidly than normal CA I.