Abbreviations: T, total weight of monomer (acrylamide and N, N-methylenebisacrylamide) per 100 ml of solvent; C, amount of N, N -methylenebisacrylamide expressed as percentage of total monomer (w/w).

Correspondence: Arvind M. Kayastha, School of Biotechnology, Faculty of Science, Banaras Hindu University, Varanasi-221 005, India

Urease from pigeonpea was entrapped in polyacrylamide gel with 50% immobilization at 10% total monomer (containing 5% cross-linker) with high mechanical stability of the gel. Approximately 0.61 mg of protein could be loaded per 5 ml of gel. The immobilized enzyme had a t_1/2 of approx. 200 days when stored in 0.1 M Tris/acetate buffer, pH 6.5, at 4 °C. The gel strips were used 4–5 times for urea assay over a period of 6 h with less than 2% loss of activity. Approximately 50% immobilization of urease in calcium alginate was observed at 3% alginate with 0.12 mg protein/ml alginate. The resultant enzyme beads showed a t_1/2 of approx. 75 days when stored in 0.1 M Tris/acetate buffer, pH 6.5, at 4 °C. The beads were used 4–5 times for urea assay over a period of 6 h with about 40% loss of activity. In both cases, the enzyme activity was directly proportional to the amount of immobilized enzyme. There was practically no leaching of the entrapped enzyme over a period of 48 h from either of the polymers. Both the immobilized enzyme preparations were used to analyse the blood urea of some clinical samples from the University hospital. The results obtained compared favourably with those obtained by the usual method employed in the clinical pathology laboratory.

Received 29 May 1997/21 July 1997; accepted 11 August 1997

© 1998 The International Union of Biochemistry and Molecular Biology