Evaluation of the effect of ammonium carbamate on the stability of proteins

Abstract

AbstractBACKGROUND: The use of the volatile salt ammonium carbamate in protein downstream processing has recently been proposed. The main advantage of using volatile salts is that they can be removed from precipitates and liquid effluents through pressure reduction or temperature increase. Although previous studies showed that ammonium carbamate is efficient as a precipitant agent, there was evidence of denaturation in some enzymes. In this work, the effect of ammonium carbamate on the stability of five enzymes was evaluated.RESULTS: Activity assays showed that α‐amylase (1,4‐α–D‐glucan glucanohydrolase, EC 3.2.1.1), lysozyme (1,4‐β‐N‐acetylmuramoylhydrolase, EC 3.2.1.17) and lipase (triacyl glycerol acyl hydrolase, EC 3.1.1.3) did not undergo activity loss in ammonium carbamate solutions with concentrations from 1.0 to 5.0 mol kg−1, whereas cellulase complex (1,4‐(1,3:14)‐β‐D‐glucan 4‐glucano‐hydrolase, EC 3.2.1.4) and peroxidase (hydrogen peroxide oxidoreductase, EC 1.11.1.7) showed an average activity loss of 55% and 44%, respectively. Precipitation assays did not show enzyme denaturation or phase separation for α‐amylase and lipase, while celullase and peroxidase precipitated with some activity reduction. Analysis of similar experiments with ammonium and sodium sulfate did not affect the activity of enzymes.CONCLUSION: Celullase and peroxidase were denatured by ammonium carbamate. While more systematic studies are not available, care must be taken in designing a protein precipitation with this salt. The results suggest that the generally accepted idea that salts that denature proteins tend to solubilize them does not hold for ammonium carbamate. Copyright © 2010 Society of Chemical Industry