Nov 1, 1976

gamma-glutamyl transpeptidase of rat intestine: localization and possible role in amino acid transport

Gastroenterology
T Q GarveyK J Isselbacher

Abstract

gamma-Glutamyl transpeptidase (gamma-GT), an enzyme possibly involved in amino acid transport, was investigated in rat small intestine using the synthetic substrate L-gamma-glutamyl-p-nitroanilide. Enzyme localization and characteristics were correlated with features of amino acid uptake. gamma-GT activity copurified with sucrase and alkaline phosphatase. Activity was maximal at pH 8.2 and was stimulated by monovalent cations. The relative specificity of the gamma-GT reaction with diglycine and eight essential amino acids as substrates correlated well with the rate of intestinal absorption of this dipeptide and these amino acids as observed by others. gamma-GT activity was 12-fold greater in the jejunum than in the ileum, again in agreement with relative rates of amino acid absorption along the length of rat intestine. The specific activity of gamma-GT in villus tip cells was 10 times greater than in crypt cells, and amino acid uptake was 2 to 6 times greater with villus tip than with crypt cells. Bromosulfophthalein, a noncompetitive inhibitor of gamma-GT, inhibited amino acid uptake. These studies support the concept that membrane gamma-GT may be involved in amino acid and dipeptide uptake, and indicate that further investiga...Continue Reading

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Mentioned in this Paper

Establishment and Maintenance of Localization
Malignant Neoplasm of Jejunum
Electrolytes
Tissue Viability
Amino Acids, I.V. solution additive
Gamma-glutamyl transferase
Small Intestinal Wall Tissue
Uptake
Ileum
Alkaline Phosphatase Measurement

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