Enzyme Technology
Nucleic acid removal
Intracellular enzyme preparations contain nucleic acids which can
give rise to increased viscosity interfering with enzyme purification
procedures, in particular ultrafiltration. Some organisms contain sufficient
nuclease activity to eliminate this problem but, otherwise, the nucleic acids
must be removed by precipitation or degraded by the addition of exogenous
nucleases. Ammonium sulphate precipitation (see later) can be effective in
removing nucleic acids but will remove some protein at the same time. Various
more specific precipitants have been used, usually positively-charged materials
which form complexes with the negatively-charged phosphate residues of the
nucleic acids. These include, in order of roughly decreasing effectiveness,
polyethyleneimine, the cationic detergent cetyltrimethyl ammonium bromide,
streptomycin sulphate and protamine sulphate. All of these are expensive and
possibly toxic, particularly streptomycin sulphate. Also, they may complex
undesirably with certain enzymes. They may be necessary, however, where possible
contamination of the enzyme product must be avoided, such as in the preparation
of restriction endonucleases. Otherwise, treatment with bovine pancreatic
nucleases is probably the most cost-effective method of nucleic acid
removal.
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This page was established in 2004 and last updated by Martin
Chaplin on
6 August, 2014
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