LOCALIZATION OF THE FRUCTOSE 1,6-BISPHOSPHATASE AT THE NUCLEAR PERIPHERY

The localization of fructose 1,6-bisphosphatase (D-Fru-1,6-P-2-1-phosp hohydrolase, EC 3.1.3.11) in rat kidney and liver was determined immun ohistochemically using a polyclonal antibody raised against the enzyme purified from pig kidney. The immunohistochemical analysis revealed t hat the bisphosphatase was preferentially localized in hepatocytes of the periportal region of the liver and was absent from the perivenous region. Fructose-1,6-bisphosphatase was also preferentially localized in the cortex of the kidney proximal tubules and was absent in the glo meruli, loops of Henle, collecting and distal tubules, and in the rena l medulta. As indicated by immunocytochemistry using light microscopy and confirmed with the use of reflection confocal microscopy, the enzy me was preferentially localized in a perinuclear position in the liver and the renal cells. Subcellular fractionation studies followed by en zyme activity assays revealed that a majority of the cellular fructose -1,6-bisphosphatase activity was associated to subcellular particulate structures. Overall, the data support the concept of metabolic zonati on in liver as well as in kidney, and establish the concept that the F ructose-1,6-bisphosphatase is a particulate enzyme that cannot be cons idered a soluble enzyme in the classical sense. (C) 1996 Wiley-Liss, I nc.