Restoration of a defective Lactococcus lactis xylose isomerase.

ABSTRACT: The genes (xylA) encoding xylose isomerase (XI) from two Lactococcus lactis subsp. lactis strains, 210 (Xyl(-)) and IO-1 (Xyl(+)), were cloned, and the activities of their expressed proteins in recombinant strains of Escherichia coli were investigated. The nucleotide and amino acid sequence homologies between the xylA genes were 98.4 and 98.6%, respectively, and only six amino acid residues differed between the two XIs. The purified IO-1 XI was soluble with K(m) and k(cat) being 2.25 mM and 184/s, respectively, while the 210 XI was insoluble and inactive. Site-directed mutagenesis on 210 xylA showed that a triple mutant possessing R202M/Y218D/V275A mutations regained XI activity and was soluble. The K(m) and k(cat) of this mutant were 4.15 mM and 141/s, respectively. One of the IO-1 XI mut

SUBMITTER: Park JH 

PROVIDER: S-EPMC444798 | biostudies-literature | 2004 Jul

REPOSITORIES: biostudies-literature