Theanine, gamma-glutamylethylamide, is metabolized by renal phosphate-independent glutaminase.
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 3.5.1.2], 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.
Tsuge
Haruhito
H
Laboratory of Nutritional Biochemistry, Department of Food Science, Faculty of Agriculture, Gifu University, 1-1 Yanagido, Japan. tsuge@cc.gifu-u.ac.jp
Sano
Sachi
S
Hayakawa
Takashi
T
Kakuda
Takami
T
Unno
Tomonori
T
D000818:Animals; D002855:Chromatography, Thin Layer; D004591:Electrophoresis, Polyacrylamide Gel; D005021:Ethylamines / Q000378:metabolism; D005971:Glutamates / Q000378:metabolism*; D018698:Glutamic Acid / Q000378:metabolism; D005972:Glutaminase / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D006033:Glycylglycine; D007527:Isoenzymes / Q000378:metabolism; D007668:Kidney / Q000201:enzymology*; D010710:Phosphates / Q000737:chemistry; D051381:Rats; D017208:Rats, Wistar; D013379:Substrate Specificity; D005723:gamma-Glutamyltransferase / Q000378:metabolism
D005021:Ethylamines; D005971:Glutamates; D007527:Isoenzymes; D010710:Phosphates; D006033:Glycylglycine; D018698:Glutamic Acid; C026166:theanine; D005723:gamma-Glutamyltransferase; D005972:Glutaminase; C041564:ethylamine