PURIFICATION AND PROPERTIES OF TAUROPINE DEHYDROGENASE FROM A RED ALGA, RHODOGLOSSUM-JAPONICUM

Tauropine dehydrogenase which is a member of 'opine' dehydrogenases an d catalyzes the reductive condensation of taurine with pyruvate was pu rified from a red alga, Rhodoglossum japonicum using a combination of ammonium sulfate fractionation, gel filtration, affinity, and ion exch ange chromatography. The molecular mass of this enzyme, obtained by HP LC using TSK SW2000G in its native form and SDS-PAGE in its denatured form, was 39000 and 42000, respectively. This means tauropine dehydrog enase has monomeric structure like other opine dehydrogenases. The rel ative activities for amino acids as substrate were 100 for taurine, 17 for valine and 12 for homotaurine. The apparent Km values for taurine , pyruvate and NADH were 15.0 mM, 0.80 mM and 0.04 mM, and for tauropi ne and NAD+ were 30 mM and 0.12 mM, respectively. Diurnal change of ta uropine content was observed in R. japonicum, tauropine increased in t he daytime and decreased in the nighttime.