PURIFICATION AND PROPERTIES OF SKIPJACK LIVER TRYPTOPHAN-HYDROXYLASE

Tryptophan hydroxylase (5-monooxygenase) (EC 1.14.16.4; Trp hyroxylase ) in skipjack liver was extracted with Tris-acetate buffer solution an d purified by acid treatment, ammonium sulfate fractionation, Sephadex G-150, DEAE-Sepharose CL-6B, Butyl-Sepharose 4B, and Toyopearl HW-55F 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 electrophor esis which also revealed that the enzyme and composed of identical sub units with a molecular weight of 97,000. The optimum temperature was 3 5-degrees-C and the enzyme was stable under 35-degrees-C. The optimum pH was 8.0 and the enzyme retained more than 80% of its original activ ity between pH 7.5 and 8.5 after incubation at 35-degrees-C for 30 min . The enzyme was inhibited by Co2+, Mn2+, and Zn2+ ions. However, it c an be activated by adding Fe3+, K+, and Li+ ions.