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Kinetic properties of gamma-glutamyltranspeptidase and leucine-amino-peptidase in developing rat intestine: effect of hormones.
Indian J Exp Biol ; 1990 Jan; 28(1): 18-22
Artículo en Inglés | IMSEAR | ID: sea-56374
ABSTRACT
Administration of cortisone and thyroxine produced adult-type increase in the activities of soluble and membrane-bound gamma-glutamyltranspeptidase (gamma-GTP) in suckling rat intestine. Membrane-bound enzyme activity remained unaltered while the soluble enzyme activity was reduced (27%) in insulin-injected pups. Kinetic analysis revealed that the observed changes in the enzyme levels were a consequence of altered Vmax with no change in apparent Km. A 2-fold increase in the Km value was observed in adult gamma-GTP activity compared to that of suckling animals. Membrane-bound and soluble gamma-GTP yielded similar values of the Ea (9.7-13.1 kcal/mole) but exhibited apparent differences in heat stability in the control and hormone-injected groups. Leucine-amino peptidase(LAP) activity was reduced to adult levels in insulin-treated suckling animals. Thyroxine- and cortisone-treatment did not affect soluble activity but significantly (P less than 0.001) augmented the membrane-bound LAP levels. This increase was due to enhanced (54-82%) Vmax with no change in Km. The observed decrease in LAP activity in response to insulin was due to reduced Vmax. There was no change in Ea (8-11.6 kcal/mole) except the value was raised to 19.1 kcal/mole in cortisone-injected pups. Both the soluble and membrane-bound LAP activities were quite resistant to heat inactivation upto 30 min at 60 degrees C except in weanling rats. Thus, the kinetic behaviour of normally developed and precociously induced gamma-GTP and LAP is essentially similar but there are apparent differences in the mode of action of insulin, cortisone and thyroxine in affecting the development of these enzymes.
Asunto(s)
Texto completo: Disponible Índice: IMSEAR (Asia Sudoriental) Asunto principal: Ratas / Ratas Endogámicas / Tiroxina / Cortisona / Cinética / Gamma-Glutamiltransferasa / Hormonas / Intestinos / Leucil Aminopeptidasa / Animales Idioma: Inglés Revista: Indian J Exp Biol Año: 1990 Tipo del documento: Artículo

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Texto completo: Disponible Índice: IMSEAR (Asia Sudoriental) Asunto principal: Ratas / Ratas Endogámicas / Tiroxina / Cortisona / Cinética / Gamma-Glutamiltransferasa / Hormonas / Intestinos / Leucil Aminopeptidasa / Animales Idioma: Inglés Revista: Indian J Exp Biol Año: 1990 Tipo del documento: Artículo