We have cloned and characterized the pykA gene from Bacillus subtilis which codes for a pyruvate kinase (PK) enzyme. This gene has been located downstream a putative phosphofructokinase gene, suggesting that they are part of the same operon. The deduced amino acid sequence of this PK showed a strong similarity to other PKs from different sources; however, as it has been found in other bacilli, the B. subtilis pykA enzyme had an extra C-terminal sequence consisting of about 112 amino acid residues. This gene was insertionally inactivated at the chromosomal level, with an antibiotic resistance marker. The analysis of this mutation in wild type and pts- backgrounds, indicated that B. subtilis has no other pyruvate kinase activity capable of complementing the absence of PykA.