Abstract

The whole gal/lac operon genes of Lactococcus lactis ssp. lactis 7962 were reported as follows: galA-galM-galK-galT-lacA-lacZ-galE. The galK gene encoding a galactokinase involved in one of the Leloir pathways for galactose metabolism was found to be 1,197 bp in length and encodes a protein of 43,822 Da calculated molecular mass. The deduced amino acid sequence showed over 50% homology with GalK proteins from several other lactic acid bacteria. The galK gene was expressed in E. coli and the product was identified as a 43 kDa protein which corresponds to the estimated size from the DNA sequence. The galactokinase activity of recombinant E. coli was about 8 times greater against that of the host strain and more than 3 times higher than the induced L. lactis 7962.

• Keywords: Lactococcus lactis ssp. lactis ATCC7962; galK; galactokinase