Glucuronidase localization

Methods for the histochemical localization of /3-glucuronidase, employing the /3-glucuronides of 1-naphthol, 6-bromo-2-naphthol, l-(2-hydroxy-phenylazo)-2-naphthol, and 8-quinolinol as substrates, have been critically examined by Burton and Pearse.146 The last-named substrate gave the least unsatisfactory results, and the technique compares not unfavorably with histochemical methods for other enzymes. 

Skorupa, A. F. et al. (1999). Sustained production of beta-glucuronidase from localized sites after AAY vector gene transfer results in widespread distribution of enzyme and reversal of lysosomal storage lesions in a large volume of brain in mucopolysaccharidosis VII mice. Exp. Neurol. 160(1), 17-27. 

Secondary metabolites can accumulate in the same cell and tissue in which they are formed, but intermediates and end-products can also be transported to other locations for further elaboration or accumulation. For example, TAs and nicotine are typically produced near the root apex, but mostly accumulate within leaf cell vacuoles. Even TA biosynthesis itself involves intercellular transport of several pathway intermediates (Fig.7.9A). P-Glucuronidase (GUS) localization in A. belladonna roots transformed with a PMT promoter-GUS fusion showed that PMT expression is restricted to the pericycle.144 Immunolocalization and in situ RNA hybridization also demonstrated the pericycle-specific expression of H6H.145,146 In contrast, TR-I was immunolocalized to the endodermis and outer root cortex, whereas TR-II was found in the pericycle, endodermis, and outer cortex.85 The localization of TR-I to a different cell type than PMT and H6H implies that an intermediate between PMT and TR-I moves from the pericycle to the endodermis (Fig.7.9A). Similarly, an intermediate between TR-I and H6H must move back to the pericycle. The occurrence of PMT in the pericycle provides the enzyme with efficient access to putrescine, ornithine, and arginine unloaded from the phloem. In the same way, scopolamine produced in the pericycle can be readily translocated to the leaves via the adjacent xylem. 

Nedocromil sodium is a mast-cell stabilizer that inhibits release of mediators from inflammatory cell types associated with asthma, including histamine from mast cells and beta-glucuronidase from macrophages. It may also suppress local production of leukotrienes and prostaglandins and inhibit development of bronchoconstriction responses to inhaled antigen and other challenges such as cold air. It is... 

The intracellular localization of exogenously supplied human platelet 3-D-glucuronidase in cultured skin fibroblasts derived from a j3-D-glucuronidase-deficient patient was studied.Four cellular fractions were obtained by... 

Histochemical assay. The best substrate currently available for histochemical localization of beta-glucuronidase activity in tissues and cells is 5-bromo-4-chloro-3-indolyl glucuronide (X-GLUC). This substrate works very well, giving a blue precipitate at the site of enzyme activity. There are niimerous variables that affect the quality of the histochemical localization. 

It is also interesting to point out that another closely related acid hydrolase, y3-glucuronidase, also has a dual localization in both microsomes... 

A mammalian system has been used to determine the fate in vivo of bovine jS-D-glucuronidase administered intravenously to mice that are deficient in the enzyme sensitive and reliable discrimination between bovine-liver and residual, murine-tissue jS-D-glucuronidase activities was achieved by inactivation of the former with heat. The bovine activity was cleared rapidly from circulation following injection, and was recovered almost exclusively in the liver, where 72% is localized in the lysosomes. The mammalian system provides an in vivo model that enables the protection and delivery of an exogenous enzyme to be evaluated prior to replacement trials in patients with inherited diseases caused by an enzyme deficiency. 

Dual localization of 3-glucuronidase in endoplasmic reticulum and lysosomes was demonstrated by Fishman et al. (1967b) by using two methods of cytobiochemistry. From these findings it has been suggested that S-glueuronidase may serve as a structural protein of the endoplasmic reticulum. 

The localization of /3-glucuronidase and other hydrolases in the tests of cat and dog has been demonstrated by Wrobcl and Kuehnel (1967). In both species the principal site of /3-glucuroiiidase is i.eydig cells. 

In newborn kidney, the reactions of /3-glucuronidase, glucose-6-phos-phatase, and leucine aminopeptidase are positive in the proximal and distal convolutions of the nephrons, but are localized only in the middle and deep regions of the cortex, while the three enzyme reactions are positive in the convoluted tubules of the cortex of the adult kidney. The cortex seems at this stage functionally inactive (Turchini et al., 1965). Some histo-chemical observation on newborn lymphosarcoma has been reported (Shiinada, 1964). 

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