Preferential localization of rat liver D-myo-inositol 1,4,5-trisphosphate/1,3,4,5-tetrakisphosphate 5-phosphatase in bile-canalicular plasma membrane and 'late' endosomal vesicles.
Previous studies have shown that most of the inositol 1,4,5-trisphosphate/inositol 1,3,4,5-tetrakisphosphate 5-phosphatase activity of rat hepatocytes is associated with the plasma membrane [Shears, Parry, Tang, Irvine, Michell & Kirk (1987) Biochem. J. 246, 139-147]. We now show that the specific activity of this enzyme is highest in the bile-canalicular domain of the plasma membrane, at the opposite pole of the hepatocyte from the presumed site of receptor-mediated formation of inositol 1,4,5-trisphosphate. In intact hepatocytes and in sealed membrane vesicles originating from the bile-canalicular domain of the plasma membrane, the 5-phosphatase activity was mostly latent and therefore located at the cytoplasmic surface. A substantial amount of 5-phosphatase was also found in rat liver endosomal fractions, particularly a 'late' endosomal subfraction, indicating that this enzyme may be transported between the sinusoidal plasma membrane and other cellular membranes.
Shears
S B
SB
Department of Biochemistry, University of Birmingham, U.K.
Evans
W H
WH
Kirk
C J
CJ
Michell
R H
RH
D000818:Animals; D001648:Bile Canaliculi / Q000201:enzymology*; D001653:Bile Ducts, Intrahepatic / Q000201:enzymology*; D002462:Cell Membrane / Q000201:enzymology; D011992:Endosomes / Q000201:enzymology*; D000072181:Inositol Polyphosphate 5-Phosphatases; D008099:Liver / Q000201:enzymology*; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*; D051381:Rats; D013347:Subcellular Fractions / Q000201:enzymology
D010744:Phosphoric Monoester Hydrolases; D000072181:Inositol Polyphosphate 5-Phosphatases; C043422:myo-inositol 1,4,5-triphosphate phosphatase