Effect of inducible thrB expression on amino acid production in Corynebacterium lactofermentum ATCC 21799

Appl Environ Microbiol. 1995 Jan;61(1):74-8. doi: 10.1128/aem.61.1.74-78.1995.


Amplification of the operon homdr-thrB encoding a feedback-insensitive homoserine dehydrogenase and a wild-type homoserine kinase in a Corynebacterium lactofermentum lysine-producing strain resulted in both homoserine and threonine accumulation, with some residual lysine production. A plasmid enabling separate transcriptional control of each gene was constructed to determine the effect of various enzyme activity ratios on metabolite accumulation. By increasing the activity of homoserine kinase relative to homoserine dehydrogenase activity, homoserine accumulation in the medium was essentially eliminated and the final threonine titer was increased by about 120%. Furthermore, a fortuitous result of the cloning strategy was an unexplained increase in homoserine dehydrogenase activity. This resulted in a further decrease in lysine production along with a concomitant increase in threonine accumulation.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Corynebacterium / genetics*
  • Corynebacterium / metabolism
  • Gene Expression Regulation, Bacterial
  • Genes, Bacterial*
  • Homoserine / biosynthesis
  • Homoserine Dehydrogenase / genetics*
  • Lysine / biosynthesis
  • Phosphotransferases (Alcohol Group Acceptor) / genetics*
  • Plasmids
  • Threonine / biosynthesis*


  • Threonine
  • Homoserine
  • Homoserine Dehydrogenase
  • Phosphotransferases (Alcohol Group Acceptor)
  • homoserine kinase
  • Lysine