TAUROPINE DEHYDROGENASE FROM THE SANDWORM ARABELLA IRICOLOR (POLYCHAETA, ERRANTIA) - PURIFICATION AND CHARACTERIZATION

This is thr first report of the purification of tauropine dehydrogenas e (NAD: tauropine oxidoreductase) from a polychaete worm. In the sandw orm Arabella iridolor Montagu (Polychaeta: Errantia), two forms of TaD H were detected: major component (pI = 7.5) and minor one (pI = 6.4). The major TaDH component was purified to homogeneity by means of (NH4) (2)SO4 precipitation, anion-exchange, affinity, chromatofocusing and h ydrophobic chromatography, and characterized. From the molecular mass of 43.7 kDa obtained by rapid gel-filtration and that of 43.5 kDa by S DS-PAGE, the sandworm enzyme appeared to he a monomeric protein. Maxim um rates of reduction of pyruvate and oxidation of tauropine were obse rved at pH 7.0 and 8.5, respectively. Pyruvate and taurine were prefer red substrate for thr enzyme. Apparent K-m values determined using con stant co-substrate concentrations were: 35.7 mM, 0.34 mM, and 0.036 mM for taurine, pyruvate: and NADH, respectively, in the tauropine synth esizing reaction; and 4.8 mM and 0.051 mM for tauropine and NAD', resp ectively, in the tauropine oxidizing reaction. The tauropine synthesiz ing reaction was subject to substrate: inhibition hy pyruvate: maximum rate was observed at 2.5-3.0 mM (inhibitory range of pyruvate concent ration producing half-maximal rate was 26.8 mM).