Biosynthesis of the branched-chain amino acids in the cyanobacterium Synechocystis PCC6803: existence of compensatory pathways

Curr Microbiol. 2002 Aug;45(2):94-8. doi: 10.1007/s00284-001-0097-2.


Complementation of an E. coli mutant auxotrophic for the branched-chain amino acids (BCAA)--valine, leucine, and isoleucine--by the ilvG gene ( slr2088) of the cyanobacterium Synechocystis PCC6803 indicates that this gene encodes an active alpha-acetohydroxy acid synthase. Differences of response of the recombinants to the addition of the essential amino acids suggested a lower specificity for the initial reaction of the valine/leucine chain than for the isoleucine one. Inactivation of ilvG in Synechocystis led to a leaky phenotype, suggesting a capacity to compensate the auxotrophies by other processes. This observation is discussed in view of the general difficulty of obtaining auxotrophs in cyanobacteria.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acids, Branched-Chain / biosynthesis*
  • Cyanobacteria / genetics
  • Cyanobacteria / metabolism*
  • Escherichia coli / genetics
  • Genetic Complementation Test
  • Isoleucine / metabolism
  • Leucine / metabolism
  • Mutation
  • Phenotype
  • Valine / metabolism


  • Amino Acids, Branched-Chain
  • Isoleucine
  • Leucine
  • Valine