INACTIVATION OF BLASTICIDIN-S BY BACILLUS-CEREUS .5. PURIFICATION ANDCHARACTERIZATION OF BLASTICIDIN-S-DEAMINASE MEDIATED BY A PLASMID FROM BLASTICIDIN-S RESISTANT BACILLUS-CEREUS-K55-S1

Blasticidin S (BS) deaminase (BSR) from a BS-resistant strain, Bacillu s cereus K55-S1, was purified to homogeneity. Molecular weights determ ined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (sos -PAGE) and by gel filtration on HPLC are about 15500 and 35000, respec tively, indicating the enzyme is a homodimer. The amino acid compositi on and N-terminal sequence of BSR are the same as those deduced from t he nucleotide sequence of the BS-resistant gene, bsr. The optimum temp erature and pH for enzyme activity are 60-65 degrees C and near 10.0, respectively. The activity of BSR is inhibited by Cu2+, Hg2+, and p-ch loromercuric benzoate (PCMB). Inhibition by PCMB or HgCl2 is reversibl e by the addition of SH reagents. The enzyme catalyzes the deamination of BS and its derivatives, but not cytosine nucleosides.