The Mycobacterium bovis BCG pang gene, encoding ketopantoate hydroxymethyltransferase (KPHMT), was cloned from a λgt11 genomic library and sequenced. The DNA sequence encodes a protein that contains 281 amino acid residues (M, 29,337) with a high similarity to the KPHMTs. Subcloning of a 846 by open reading frame (ORF), but not a 735 by ORF, into the vector pUC19 led to complementation of the panB mutant of Escherichia coli. The BCG pang gene was overeacpressed in E. coli and the KPHMT purified to homogeneity The recombinant protein was further confirmed by an enzymatic assay.