Rhodanese, a cyanide detoxifying enzyme, was isolated from soldier termite using ammonium sulphate fractionation, reactive blue affinity chromatography and gel filtration on Sephadex G-150. The enzyme had a specific activity of 7.9 RU per milligram of protein. The K m values of the substrates (KCN and Na 2 S 2 O 3 ) were 7.0 mM and 5.3 mM respectively. The results of substrate specificity showed that the enzyme was specific for thiosulphate (S 2 O 3 2-) when compared with other sulphur compounds. The native and subunit molecular weight of the enzyme was found to be 37,154 and 32,210 dalton respectively. The optimum pH and temperature of the enzyme activity were 8.0 and 55 o C respectively. NH 4 + , Mn 2+ , and Ba 2+ had about 50 % effect on the activity of the enzyme. However, Hg 2+ , Zn 2+ and Mg 2+ inhibited the enzyme considerably (≤ 20 %). The half-life of the enzyme at 40 o C, 50 o C, 60 o C, 70 o C and 80 o C were found to be 150.7, 60.3, 43.0, 37.7 and 37.0 respectively.
Arginase (EC 3.5.3.1) catalyzes the hydrolysis of arginine to ornithine and urea. Arginase was purified and characterized from the gut of Zonocerus variegatus through DEAE-cellulose and biogel-P100 gel filtration chromatography. The specific activity of the enzyme was 3.7 µmoles/min per mg of protein and a yield of 14.7%. An apparent molecular weight of 143,000 daltons was estimated by gel filtration on biogel P-100. The Michaelis constant (K m) of the enzyme was 40 mM with arginine as substrate. The optimum pH was 8.0 and the optimum temperature was 40 o C for Z. variegatus arginase. The enzyme was stable up to 40 o C for 20 min and lost all of its activity at 80 o C. The enzyme was specific for arginine as substrate. The enzyme was strongly enhanced in the presence of Mn 2+ , Na + , NH 4 + and Hg 2+ showed similar activation. Ni 2+ and Zn 2+ slightly inhibited Z. variegatus. Chelating (EDTA, citrate, ascorbic acid and urea) and thio (2-mercaptoethanol and cystein) compounds inhibited the activity of arginase in Z. variegatus. While amino acids (proline, lysine, aspartate and valine) showed no inhibition on arginase activity. The presence of arginase in the gut of Zonocerus variegatus could be for other functions rather than urea production in urea cycle.
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