Evolution of glutamate dehydrogenase regulation of insulin homeostasis is an example of molecular exaptation

Biochemistry. 2004 Nov 16;43(45):14431-43. doi: 10.1021/bi048817i.


Glutamate dehydrogenase (GDH) is found in all organisms and catalyzes the oxidative deamination of glutamate to 2-oxoglutarate. While this enzyme does not exhibit allosteric regulation in plants, bacteria, or fungi, its activity is tightly controlled by a number of compounds in mammals. We have previously shown that this regulation plays an important role in insulin homeostasis in humans and evolved concomitantly with a 48-residue "antenna" structure. As shown here, the antenna and some of the allosteric regulation first appears in the Ciliates. This primitive regulation is mediated by fatty acids and likely reflects the gradual movement of fatty acid oxidation from the peroxisomes to the mitochondria as the Ciliates evolved away from plants, fungi, and other protists. Mutagenesis studies where the antenna is deleted support this contention by demonstrating that the antenna is essential for fatty acid regulation. When the antenna from the Ciliates is spliced onto human GDH, it was found to fully communicate all aspects of mammalian regulation. Therefore, we propose that glutamate dehydrogenase regulation of insulin secretion is a example of exaptation at the molecular level where the antenna and associated fatty acid regulation was created to accommodate the changes in organelle function in the Ciliates and then later used to link amino acid catabolism and/or regulation of intracellular glutamate/glutamine levels in the pancreatic beta cells with insulin homeostasis in mammals.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adenosine Diphosphate / analogs & derivatives*
  • Adenosine Diphosphate / chemistry
  • Adenosine Diphosphate / metabolism
  • Alanine / genetics
  • Allosteric Regulation / genetics
  • Animals
  • Arginine / genetics
  • Cattle
  • Deamination
  • Evolution, Molecular*
  • Glutamate Dehydrogenase / antagonists & inhibitors
  • Glutamate Dehydrogenase / chemistry*
  • Glutamate Dehydrogenase / genetics
  • Glutamate Dehydrogenase / metabolism
  • Homeostasis* / genetics
  • Humans
  • Insulin / metabolism*
  • Insulin Secretion
  • Kinetics
  • Lipid Peroxidation
  • Palmitoyl Coenzyme A / chemistry
  • Protein Binding
  • Sequence Alignment
  • Sequence Homology, Amino Acid
  • Substrate Specificity
  • Tetrahymena thermophila / enzymology
  • Tetrahymena thermophila / genetics


  • Insulin
  • Palmitoyl Coenzyme A
  • Adenosine Diphosphate
  • 2',3'-(O-(2,4,6-trinitrocyclohexadienylidine))adenosine 5'-diphosphate
  • Arginine
  • Glutamate Dehydrogenase
  • Alanine