Abstract
Tryptophan hydroxylase (5-monooxygenase) (EC 1. 14. 16. 4; Trp hydroxylase) in skipjack liver was extracted with Tris-acetate buffer solution and purified by acid treatment, ammonium sulfate fractionation, Sephadex G-150, DEAE-Sepharose CL-6 B, Butyl-Sepharose 4 B, and Toyopearl HW-55 F chromatography. The enzyme was purified 1, 500-fold with a 6.2% yield from skipjack liver. The apparent molecular weight was estimated to be 288, 000 by gel filtration on Sephadex G-150. The enzyme gave a single protein band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis which also revealed that the enzyme was composed of identical subunits with a molecular weight of 97, 000. The optimum temperature was 35°C and the enzyme was stable under 35°C. The optimum pH was 8.0 and the enzyme retained more than 80% of its original activity between pH 7.5 and 8.5 after incubation at 35°C for 30min. The enzyme was inhibited by Co2+, Mn2+, and Zn2+ ions. However, it can be activated by adding Fe3+, K+, and Li+ ions.
