The giant African snails (Archachatina marginata) are herbivorous tropical gastropods. They are commonly located in areas littered with decaying vegetable matters which they feed on. When the haemolyph of this organism was passed through Sephadex G-200, the resin was digested. The ability of snails to digest vegetable matters and the digestion of Sephadex G-200 resin by the haemolyph led to the suspicion of the presence of cellulase in snail haemolyph. Cellulase from haemolyph of the giant African snail was purified to homogeneity by a combination of gel filtration on BioGel P-300 and ionexchange chromatography on DEAE-Sephadex. The homogeneity of the pure enzyme was adjudged by polyacrylamide gel electrophoresis in the absence and presence of sodium dodecyl sulphate. The subunit molecular weight was 16,875±1,556 daltons and the apparent molecular weight as determined by gel filtration was 52,000 daltons. Thus, the enzyme is at least a dimer. The enzyme had a specific activity of 1359.09 units/mg of protein. The Michaelis-Menten constant (K m) for carboxymethyl (CM)cellulose was 5.17± 0.74 mg/ml and the maximum velocity (V max) was 1067±195 units/ml. The enzyme did not degrade salicin, cellobiose and o-nitrophenyl-β-D-glucopyranoside. In addition, its activities towards filter paper and cotton wool were insignificant compared with its activity towards CM-Cellulose. Linamarin was found to inhibit the action of the enzyme to about 18%. The high specificity for CMcellulose and the rapid decrease in the viscosity of CM-cellulose suggests that the enzyme is likely an endoglucanase.

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The study investigates the purification and characterisation of rhodanese from the liver of the tilapia fish (Oreochromis niloticus) collected from Asejire Lake in Nigeria. This was with a view to understanding the biochemical basis of the survival of the fish in cyanide polluted water. Rhodanese was isolated and purified from liver tissue homogenate of tilapia using CM-Sephadex ion exchange chromatography and Sephadex G-75 gel filtration. The specific activity of the enzyme was 56.86 U/mg. The K m values for KCN and Na 2 S 2 O 3 as substrates were 0.1240 ± 0.0021 mM and 0.0516 ± 0.0097 mM, respectively. The apparent molecular weight was estimated by gel filtration on a Sephacyl S-400 column to be 35,460 Da. The optimal activity was found at pH 6.5 and the temperature optimum was 40°C. The rhodanese enzyme showed that the activity of the enzyme was not affected by MgCl 2 , KCl, NH 4 Cl, MnCl 2 and CaCl 2 while AlCl 3 , inhibited the enzyme.

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