Cytosine Deaminase from Escherichia coli-Production, Purification, and Some Characteristics

Abstract

We wanted to obtain a large amount of cytosine deaminase from Escherichia coli. This enzyme deaminates 5-fluorocytosine and is thermostable. It is needed for trial use in a novel chemotherapy for cancer in combination with 5-fluorocytosine. We improved the conditions of its production by examining the culture conditions. A pH-stat culture with the culture pH controlled at around 8.5 using citric acid gave efficient production of cell mass and enzyme activity. The enzyme was purified 1200-fold from the cell-free extract, to homogeneity, using two kinds of affinity adsorbents prepared for this purpose. The enzyme had a molecular weight of 200, 000 (gel permeation), and seemed to be an SH-enzyme. The purified enzyme was thermostable.