Lamivudine production via enantioselective deamination by thermostable Bacillus caldolyticus cytidine deaminase

To decrease the costs of producing the anti-HIV drug, lamivudine, an enzymatic conversion process was developed instead of the traditional chemical method. Thermostable cytidine deaminase was over-produced by cloning the cdd gene into E. coli JF611/pCJH53 from Bacillus caldolyticus. The purified cytidine deaminase was recovered from the lysate of the recombinant E. coli JF611/pCJH53 by removing heat-denatured proteins and eluting sequential chromatography. When the enzyme was used to deaminate (–)--l-(2R, 5S)- and (+)--d-(2S, 5R)-1, 3-oxathiolanyl-cytosine, about 68% of the (+)--d-(2S, 5R)-1, 3-oxathiolanyl-cytosine was deaminated into the corresponding (+)-thiauridine maximally.