The gene from Bacillus brevis TT02-8 encoding arginase was cloned into Escherichia coli, and its nucleotide sequence was identified. The nucleotide sequence contained an open reading frame that encoded a polypeptide of 298 amino acid residues with a predicted molecular weight of 31,891, which was consistent with that previously calculated for arginase purified from this bacterium. Comparison of the deduced amino acid sequence of the B. brevis TT02-8 arginase with that of the prokaryotic and eukaryotic arginases of Bacillus caldovelox, Bacillus subtilis, Agrobacterium Ti plasmid C58, Saccharomyces cerevisiae, Coccidioides immitis, Xenopus laevis, Rana catesbeiana, rat liver, and human liver, showed 33-66% of the sequences to be similar; there were several highly conserved regions. Arginase activity was detected in Escherichia coli cells transformed with an expression plasmid of the cloned arginase gene.