The relative effects of some elements on the DNS method in cellulase assay

For evaluating the relative effects of some polluting salts on the measurement of cellulase activity assayed by 3,5-dinitrosalicylate (DNS) this study was done. Glucose and cellulase solutions have been treated with salts. Exoglucanase and endoglucanase were assayed by 3,5-dinitrosalicylate reagent. Measurement of reducing sugar by DNS indicator in the presence of Ca⁺², Ba⁺², Fe⁺³, Mn⁺², Pb⁺², Fe⁺², Ag+1, Zn⁺², Co⁺², and Al⁺³ salts overestimated and in the presence of Mg⁺², Cu⁺², Cd⁺², and Hg⁺² salts underestimated the real contents. The intensity of DNS color and/or the reducing power of glucose increased by decreasing radius of hydrated cation of alkaline-earth elements (from Mg⁺² to Ba⁺²) in glucose solution. Exoglucanase and endoglucanase activities increased in the presence of Na⁺, K⁺, Ca⁺², Ba⁺² and Mn⁺² salts and decreased in the presence of NH₄⁺ and Mg⁺² salts. Among the trace elements studied, Fe⁺³, Pb⁺², Fe⁺², Ag⁺¹, Zn⁺², Co⁺², and Al⁺³ were the most effective inhibitors of cellulase activity. These ions inhibited exoglucanase more than endoglucanase. The effect of most ions on cellulase activity may be related to negative or positive effect of them on the method of cellulase assessment. So, for a better data interpretation in the study of ion effects on the soil enzyme activity, both the effects of ions on the method of enzyme assay, and the effects of ions on the enzyme activity should be studied.