Abstract:The numbers of tryptophane residues in spinach CF1-ATPase were measured by means of chemical modification with N-bromosuccinimide (NBS) and photooxidation. There are 3.5 tryptophane residues in CF1-ATPase, among which two are essential for the enzyme activity. Photooxidation of CF1-ATPase led to increased O2 uptake of the reaction system and loss in activity of CF1-ATPase . Immunological property of CF1-ATPase has been altered by chemical modification with NBS and photooxidation. The resuits show that tryptophane residues seen to be essential for activity and antigenic properties of CF1-ATPase.