PROSITE documentation PDOC00643
Alpha-isopropylmalate and homocitrate synthases signatures


The following enzymes have been shown [1] to be functionally as well as evolutionary related:

  • α-isopropylmalate synthase (EC which catalyzes the first step in the biosynthesis of leucine, the condensation of acetyl-CoA and α- ketoisovalerate to form 2-isopropylmalate synthase.
  • Homocitrate synthase (EC (gene nifV) which is involved in the biosynthesis of the iron-molybdenum cofactor of nitrogenase and catalyzes the condensation of acetyl-CoA and α-ketoglutarate into homocitrate.
  • Soybean late nodulin 56.
  • Methanococcus jannaschii hypothetical proteins MJ0503, MJ1195 and MJ1392.

We have selected two conserved regions as signature patterns for these enzymes. The first region is located in the N-terminal section while the second region is located in the central section and contains two conserved histidine residues which could be implicated in the catalytic mechanism.

Last update:

April 2006 / Pattern revised.


Technical section

PROSITE methods (with tools and information) covered by this documentation:

AIPM_HOMOCIT_SYNTH_1, PS00815; Alpha-isopropylmalate and homocitrate synthases signature 1  (PATTERN)

AIPM_HOMOCIT_SYNTH_2, PS00816; Alpha-isopropylmalate and homocitrate synthases signature 2  (PATTERN)


1AuthorsWang S.-Z. Dean D.R. Chen J.S. Johnson J.L.
TitleThe N-terminal and C-terminal portions of NifV are encoded by two different genes in Clostridium pasteurianum.
SourceJ. Bacteriol. 173:3041-3046(1991).
PubMed ID2022611

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