Enzymatic Background for the Reversion or Stabilization of an L-Leucine Producing Strain of Corynebacterium glutamicum

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The enzymatic background for the reversion or stabilization of an L-leucine producer, Corynebacterium glutamicum H-1204, was examined as to the activities of α-acetohydroxy acid synthetase (AHAS) and α-isopropylmalate synthetase (IPMS), which are the key enzymes for the L-valine and L-leucine biosynthetic pathways branching from a common precursor, respectively.IPMS was derepressed and desensitized to L-leucine in strain L-76 (having the same properties as H-1204) and a stabilized strain, AB-47. In contrast, AHAS was derepressed only in strain AB-47. These results clarified enzymatically that the specific enhancement of L-leucine biosynthesis induced the depletion of L-valine, which caused reversion, and also the balanced metabolism was of great importance for the breeding of a stable amino acid producer.