Theanine, gamma-glutamylethylamide, is metabolized by renal phosphate-independent glutaminase

Biochim Biophys Acta. 2003 Mar 17;1620(1-3):47-53. doi: 10.1016/s0304-4165(02)00504-4.


The distribution of theanine-degrading activity in Wistar rats was examined and this activity was detected only in the kidney. Judging from polyacrylamide gel electrophoresis, theanine-degrading enzyme from rat kidney was purified almost to homogeneity. Theanine-degrading activity was co-purified with glutaminase activity, and the relative activity for theanine was about 85% of that for L-glutamine throughout purification. Substrate specificity of purified enzyme preparation coincided well with the data of phosphate-independent glutaminase [EC], which had been previously reported. It was very curious that gamma-glutamyl methyl and ethyl esters were more effectively hydrolyzed than theanine and L-glutamine, in view of relative activity and K(m) value. It was suggested that gamma-glutamyl moiety in theanine molecule was transferred to form gamma-glutamylglycylglycine with relative ease in the presence of glycylglycine. On the other hand, purified phosphate-dependent glutaminase did not show theanine-degrading activity at all. Thus, it was concluded that theanine was hydrolyzed by phosphate-independent glutaminase in kidney and suggested that, as for the metabolic fate of theanine, its glutamyl moiety might be transferred by means of gamma-glutamyl transpeptidase reaction to other peptides in vivo.

MeSH terms

  • Animals
  • Chromatography, Thin Layer
  • Electrophoresis, Polyacrylamide Gel
  • Ethylamines / metabolism
  • Glutamates / metabolism*
  • Glutamic Acid / metabolism
  • Glutaminase / chemistry
  • Glutaminase / isolation & purification
  • Glutaminase / metabolism*
  • Glycylglycine
  • Isoenzymes / metabolism
  • Kidney / enzymology*
  • Phosphates / chemistry
  • Rats
  • Rats, Wistar
  • Substrate Specificity
  • gamma-Glutamyltransferase / metabolism


  • Ethylamines
  • Glutamates
  • Isoenzymes
  • Phosphates
  • Glycylglycine
  • Glutamic Acid
  • theanine
  • gamma-Glutamyltransferase
  • Glutaminase
  • ethylamine