Pantothenate production in Escherichia coli K12 by enhanced expression of the panE gene encoding ketopantoate reductase

Using gene replacement and transposon Tn 5 mutagenesis, an Escherichia coli ilvC panE double mutant completely lacking ketopantoate reductase activity was isolated. This E. coli double mutant was employed to isolate the E. coli panE gene by genetic complementation. The E. coli panE gene is characterized by a 912 bp coding region, which specifies a protein of 303 amino acids with a deduced molecular mass of 33.8 kD. A panE expression plasmid carrying the panE gene under the control of the tac promotor was constructed. Introduction of the panE expression plasmid into E. coli resulted in a threefold increase in ketopantoate reductase activity. It was also shown that the enhanced panE expression in E. coli K12 led to 3.5-fold increase in pantothenate excretion. Pantothenate excretion could even be more enhanced when the growth medium was supplemented with ketopantoate.