Presence of rhodanese in the cytosolic fraction of the fruit bat (Eidolon helvum) liver

Rhodanese was isolated and purified from the cytosolic fraction of liver tissue homogenate of the fruit bat, Eidolon helvum, by using ammonium sulphate precipitation and CM-Sephadex C-50 ion exchange chromatography. The specific activity was increased 130-fold with a 53% recovery. The Km values for KCN and Na2S2O3 as substrates were 135 ± 2.2 mM and 195 ± 0.7 mM, respectively. The apparent molecular weight was estimated by gel filtration on a Sephadex G-100 column to be 36,000 Da. The optimal activity was found at a high pH (pH 9.0) and the temperature optimum was 35°C. An Arrhenius plot of the heat stability data consisted of two linear segments with a break occurring at 35°C. The apparent activation energy values from these slopes were 11.5 kcal/mol and 76.6 kcal/ mol. Inhibition studies on the enzyme with a number of cations showed that Mg2+, Mn2+, Ca2+, and Co2+ did not affect the activity of the enzyme, but Hg2+ and Ba2+ inhibited the enzyme.