Determination of CAT concentration

The concentration of purified CAT samples was determined by absorption measurements at 280 nm (Stoscheck, 1990). For CAT_III, a molar extinction coefficient e_M,280 = 32.7 x 10³ cm^-1 M^-1 (Ellis et al., 1991a) was used. The CAT_I extinction coefficient of e_M,280 = 43.1 x 10³ cm^-1 M^-1 was calculated according to the method of Gill and von Hippel (1989).