Project Details


Glutamine plays an important biosynthetic role in all mammalian cells.
Glutamine is used by the liver during diabetes, the kidney during
metabolic acidosis and the mammary gland during lactation, it is also a
major respiratory fuel for many rapidly dividing cells including cancer
cells. The major enzymes of glutamine catabolism in mammalian tissues
are two isozymes of phosphate activated glutaminase. The liver type is
found exclusively in adult liver while the other enzyme (kidney-type) is
found in all other glutamine utilizing tissues, including fetal liver and
hepatoma cells. The aim of the work described is to characterize and
understand the role and regulation of phosphate activated glutaminase in
rat liver.

This work stems from the observation that hepatic glutaminase activity is
increased 4-fold during streptozotocin diabetes. The enzyme has been
purified, specific antibodies raised against it and used to identify a
putative cDNA. The identify of the cDNA will be confirmed by comparison
of the DNA and amino acid sequences, hybrid selection of mRNA and
analysis of fusion peptide. The cDNA will be used to determine the
relative abundance of mRNA and the rate of transcription hepatic
glutaminase gene in liver from control and diabetic rats. Extracellular
stimuli involved in the regulation of hepatic glutaminase gene expression
will be identified using isolated hepatocytes and hepatoma cells.

The cDNA will be used to identify genomic sequences encoding liver-type
glutaminase and other glutamine utilizing enzymes. The distribution of
liver- and kidney-type glutaminase (activity, protein and mRNA) will be
determined in different hepatoma cells and in rat liver at different
stages of development. Chromatin structure will be analyzed in cells
showing differential expression of the two genes. These systems offer a
unique model for the study of tissue-specific, hormonal and developmental
regulation of glutaminase gene expression. The results will provide
valuable insights into why there are two enzymes and what their functions
are in the different cell types.
Effective start/end date12/31/8912/31/92


  • National Institute of Diabetes and Digestive and Kidney Diseases
  • National Institute of Diabetes and Digestive and Kidney Diseases
  • National Institute of Diabetes and Digestive and Kidney Diseases


  • Medicine(all)
  • Genetics
  • Molecular Biology


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