ISOLATION OF A BETA-GALACTOSIDASE-ENCODING GENE FROM BACILLUS-LICHENIFORMIS - PURIFICATION AND CHARACTERIZATION OF THE RECOMBINANT ENZYME EXPRESSED IN ESCHERICHIA-COLI

The Bacillus licheniformis beta-galactosidase gene, lacBl, was cloned on a 5.8-kb HindIII fragment into pBR322 and expressed by its own prom oter in Escherichia coli. Deletion and complementation analysis showed that the enzyme-encoding region was located on a 4.1-kb HindIII-ClaI fragment. The transcription region for the lacBl was identified on thi s fragment with promoter-and terminator-probe plasmids. The deduced se quence of 149 aa of the N-terminal part of lacBl showed aa sequence ho mology with beta-Gal from B, stearothermophilus, B. circulans, Halofer ax alicantei, Clostridium perfringens, Arthrobacter sp., No significan t homology was shared with those found in the lacZ and lacS families. The recombinant beta-galactosidase (LacB1) was purified by FPLC. The m olecular mass of the enzyme (80 kDa) and its optimal pH (5.7) and temp erature (45 degrees C) were determined.