Addition of p-nitrophenol and UDP-glucuronic acid to rat hepatic microsomes enhanced the MgATP-stimulated Ca2+ sequestration. This stimulatory effect was more explicit in the presence of the activator of glucuronidation, UDP-N-acetylglucosamine. The stimulation of Ca2+ uptake was dependent on the p-nitrophenol concentration and showed a good correlation with the rate of p-nitrophenol glucuronidation. The stimulation of Ca2+ sequestration was probably due to its coaccumulation with the intraluminar Pi originated during glucuronidation. The increase in extravesicular osmolarity due to the addition of UDP-glucuronic acid to microsomes resuspended in an hyposmotic medium caused a rapid and prolonged shrinking as revealed by light-scattering measurements. This indicates a poor permeability of microsomal membrane to UDP-glucuronic acid. The subsequent addition of the pore-forming compound alamethicin resulted in an immediate swelling of vesicles indicating a rapid entry of UDP-glucuronic acid. Alamethicin also caused an about 15-fold increase in p-nitrophenol UDP-glucuronosyltransferase activity. These results support the hypothesis of the intravesicular compartmentation of the microsomal UDP-glucuronosyltransferase catalytic site. © 1994 Academic Press, Inc.

Fulceri, R., Bánhegyi, G., Gamberucci, A., Giunti, R., Mandl, J., Benedetti, A. (1994). Evidence for the intraluminal positioning of p-nitrophenol UDP-glucuronosyltransferase activity in rat liver microsomal vesicles. ARCHIVES OF BIOCHEMISTRY AND BIOPHYSICS, 309(1), 43-46 [10.1006/abbi.1994.1081].

Evidence for the intraluminal positioning of p-nitrophenol UDP-glucuronosyltransferase activity in rat liver microsomal vesicles

Fulceri, R.;Gamberucci, A.;Giunti, R.;Benedetti, A.
1994-01-01

Abstract

Addition of p-nitrophenol and UDP-glucuronic acid to rat hepatic microsomes enhanced the MgATP-stimulated Ca2+ sequestration. This stimulatory effect was more explicit in the presence of the activator of glucuronidation, UDP-N-acetylglucosamine. The stimulation of Ca2+ uptake was dependent on the p-nitrophenol concentration and showed a good correlation with the rate of p-nitrophenol glucuronidation. The stimulation of Ca2+ sequestration was probably due to its coaccumulation with the intraluminar Pi originated during glucuronidation. The increase in extravesicular osmolarity due to the addition of UDP-glucuronic acid to microsomes resuspended in an hyposmotic medium caused a rapid and prolonged shrinking as revealed by light-scattering measurements. This indicates a poor permeability of microsomal membrane to UDP-glucuronic acid. The subsequent addition of the pore-forming compound alamethicin resulted in an immediate swelling of vesicles indicating a rapid entry of UDP-glucuronic acid. Alamethicin also caused an about 15-fold increase in p-nitrophenol UDP-glucuronosyltransferase activity. These results support the hypothesis of the intravesicular compartmentation of the microsomal UDP-glucuronosyltransferase catalytic site. © 1994 Academic Press, Inc.
1994
Fulceri, R., Bánhegyi, G., Gamberucci, A., Giunti, R., Mandl, J., Benedetti, A. (1994). Evidence for the intraluminal positioning of p-nitrophenol UDP-glucuronosyltransferase activity in rat liver microsomal vesicles. ARCHIVES OF BIOCHEMISTRY AND BIOPHYSICS, 309(1), 43-46 [10.1006/abbi.1994.1081].
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11365/28280
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