Isolation and kinetic properties of soldier termite (Amitermes silvestrianus Light, 1930) rhodanese

Abstract

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.

Physicochemical properties of rhodanese: A cyanide detoxifying enzyme from Pentadiplandra brazzeana (Baill) root

“…A pH range of 8.0 to 11.5 has been reported in various works (Chew and Boey, 1972;Lee et al, 1995;Agboola and Okonji, 2004;Okonji et al, 2010). The pH optimum of 8.5 was obtained for rhodanese from the liver of land tortoise (Aladesanmi et al, 2009).…”

Physicochemical properties of rhodanese from the kidney of cane rat (Thryonomys swinderianus)

“…A value of 1.076 µmole/min/mg was reported for mouse liver rhodanese (Lee et al 1995). Okonji et al, (2010b) also obtained a value of 8.4 µmole/min/mg for rhodanese from the liver of mudskipper. T. swinderianus kidney rhodanese has low specific activity.…”

“…The optimum temperature of 50 and 55°C were reported for bovine liver and Trichoderma strain rhodanese respectively (Sorbo, 1953b;Ezzi et al, 2003). Okonji et al, (2010b) obtained an optimum temperature of 55°C for soldier termite rhodanese. The optimum temperature of 50°C for T. swinderianus rhodanese indicates that the enzyme could endure a harsh condition.…”

“…The enzyme had a specific activity of 1.43 µmole/min/mg of protein and 55% recovery. Different specific activity values have been reported for rhodanese from various sources (Aladesanmi et al, 2009;Okonji et al, 2010b). A value of 1.076 µmole/min/mg was reported for mouse liver rhodanese (Lee et al 1995).…”

“…Also, the effect of metals showed that metal ions such as Na + , Fe 3+ had no inhibitory effect on T. swinderianus rhodanese activity while Hg 2+ had an inhibitory effect on the enzyme activity. Okonji et al, (2010b) reported the inhibition of soldier termite rhodanese by Hg 2+ and Mn 2+ . The absence of inhibitory effect of metal ions such as Na + , Fe 3+ observed in this study may be due to constant exposure of the animal to these metal ions from inorganic fertilizers, pesticides and other compounds used in the cultivation of food crops on which the animal feed.…”