Some Biochemical Properties of Liver Rhodanese (E. C. 2. 8. 1.1) Isolated from a Typical Marine Fish (Lutjanus goreensis)

Rhodanese is a multifunctional, mitochondrial enzyme which primary function is the protection of the electron transport system from the deleterious effect of cyanide. It carries out the said primary function, by catalyzing the conversion of the cyanide to thiocyanate, a less toxic compound. The enzyme is also implicated in preventing the formation of inorganic sulfide, a highly neurotoxic substance and in the synthesis of sulfur- containing macromolecules. The activity of the ubiquitous enzyme has been reported in soil, bacteria, plants and animal tissues. The aim of this research is to establish the presence of the cyanide detoxifying enzyme, Rhodanese, in marine aquatic life, especially in the liver of a typical marine fish, Lutjanus goreensis that subsists on other fishes and shrimps which in turn, feed on planktons and some lower organisms of the aquatic food chain. The fish liver Rhodanese, purified 11.4 fold with activity recovery of 9.03 %, had a specific activity of 19.7Mmin-1mg-1 enzyme protein. The invitro cyanide detoxifying enzyme, thiosulphate sulphur transferase (E. C.2.8.1.1), followed a non-sequential ping-pong mechanism in the formation of thiocyanate from cyanide and thiosulphate. From the kinetic studies, the Vmax of the enzyme catalysis was 5.0M/minute while the Km values for thiosulfate and cyanide were 5.88mM and 11.11mM respectively. The optimum pH of the fish liver Rhodanese enzyme was 8.2, with the pH range of 8.0 to 8.4. The optimum temperature of the enzyme was 350C. The molecular weight of the fish liver Rhodanese was 37, 153 daltons, using the gel filtration technique. From the foregoing, it is evident that the Rhodanese enzyme is present in the liver of the tropical marine fish with an appreciable activity level that is possibly attributable to the feeding habit of the fish.