A bovine serum albumin-catalase conjugate was prepared using a heterobifunctional reagent, N-succinimidyl 3-(2-pyridyldithio)propionate. The purified conjugate had an M-r of 380 kDa. The half-life time of the conjugate was 6, 69 and 65 min after heat treatment, urea treatment and trypsin hydrolysis, respectively, whereas that of native catalase was 3, 22, 28 min, respectively.