| 摘要 |
<p>Preparing L-asparaginase (I) from Escherichia coli B cells by lysis pref. of the dry cells of E. coli prepd. by lyophilisation or pref. by acetone drying. Lysis or cell rupture can be effected ultrasonically or in a colloid mill; the preferred method is by treatment with lysozyme in a buffer between pH 5 and 9 with removal of the cell debris by filtration or centrifugation. The cell-free extract is treated with ribonuclease and/or deoxyribonuclease at 0.1-10 mu g/ml. (pref. 0.25-0.5 mu g/ml). Unwanted protein is pptd. by addn. of MnCl2 and (NH4)2SO4 and centrifuged off and the enzyme isolated from the supernatant by fractional pptn. with acetone.</p> |
