Purification and characterization of mouse kidney beta-glucuronidase

Purification, biochemical and biophysical characterization of lysosomal β-D-glucuronidase from an edible freshwater mussel, Lamellidens corrianus

A lysosomal glycosidase, β-glucuronidase, has been purified to homogeneity, from the soluble extracts of a freshwater mussel, L. corrianus, by a series of chromatography techniques involving phenyl-Sepharose, ion exchange, affinity and gel filtration chromatography. In native PAGE, β-glucuronidase resolved into a single band and the molecular mass determined by gel filtration chromatography was found to be 250 kDa. Zymogram analysis with 4-methyl umbelliferyl β-glucuronide substrate validated the purified enzyme as β-glucuronidase. In SDS-PAGE, the purified enzyme was resolved into four sub-units with molecular weights around 90, 75, 65, and 50 kDa, respectively, and two of the subunits (90 and 50 kDa) cross-reacted with human β-glucuronidase antiserum. The optimum pH and temperature of the purified glycosidase were 5.0 and 70 °C, respectively. The enzyme kinetics parameters, substrate affinity (K_M) and maximum velocity (V_max) of the purified protein estimated with p-nitrophenyl β-D-glucuronide were 0.457 mM and 0.11867 μmol^-1 min^-1 mL^-1, respectively. The secondary structure of β-glucuronidase was determined in the far-UV range (190 nm to 230 nm) using CD spectroscopy. Heat denaturation plots determined by CD spectroscopy showed that the purified enzyme was stable up to 70 °C.

Overestimation of flavonoid aglycones as a result of the ex vivo deconjugation of glucuronides by the tissue β-glucuronidase

Flavonoid glucuronides are the main circulating metabolites of flavonoids in humans and animals. There has been a growing interest in the biological function of glucuronides. In order to differentiate biological activity and to assess efficacy it is essential to accurately determine the levels of flavonoid aglycone and metabolic conjugate in vivo. Many organs and body fluids of humans and animals exhibit β-glucuronidase against flavonoid glucuronides. Studies have shown that β-glucuronidase within the tissues hydrolyzes glucuronides to their aglycones during the tissue extraction, leading to artificially higher reported tissue levels of aglycone than actual in vivo concentrations. The aims of this study were to estimate the extent by which the aglycones were overestimated and to investigate the use of saccharo-1,4-lactone, a β-glucuronidase inhibitor, to block the ex vivo hydrolysis of flavonoid glucuronides. Our data demonstrate that in mouse liver tissues and human tumor xenografts levels of quercetin and methylated quercetin aglycones could be over-estimated by 7-fold. The inhibition of deconjugation of quercetin and baicalein glucuronides by saccharo-1,4-lactone is dose-dependent. The amount of saccharo-1,4-lactone used to produce optimal inhibition of the enzyme activity is in the range of 15-24μmol per gram of liver tissue. The use of β-glucuronidase inhibitor blocks the ex vivo deconjugation resulting in an accurate estimation of tissue levels of aglycone and conjugate. Our study described here can be extended to other animal models and human studies with different types of substrates of β-glucuronidase.

Characterization of the new beta-glucuronidase from Streptococcus equi subsp. zooepidemicus

Recently, a new gene encoding beta-glucuronidase from Streptococcus equi subsp. zooepidemicus (SEZ) was identified and expressed in Escherichia coli. In this paper, the characterization of the enzyme is described. Specific enzyme activity was 120,000 U/mg purified protein at 37 degrees C and pH = 7.0. The temperature and pH value, at which the enzyme has the highest specific activity, were determined and were found to be approximately 52 degrees C and 5.6, respectively. The mutant strain SEZ glcHis was designed for the efficient isolation of beta-glucuronidase from S. equi subsp. zooepidemicus. It was observed that the specific activity of beta-glucuronidase in the cytoplasmic extract of a mutated strain was about 45% lower than in the cytoplasmic extract of a wild-type strain. The specific activity of purified beta-glucuronidase from SEZ glcHis was four times as low as beta-glucuronidase purified from E. coli. Comparing the specific activity of purified streptococcal beta-glucuronidase from E. coli with E. coli beta-glucuronidase (the enzyme with the highest specific activity was supplied by Sigma), the former is 1.8 higher than the latter.

Plant endogenous beta-glucuronidase activity: how to avoid interference with the use of the E. coli beta-glucuronidase as a reporter gene in transgenic plants

We have detected a plant beta-glucuronidase activity, present in several tissues and organs of plant species belonging to different families. The fluorimetric beta-glucuronidase assay was used to partially characterize this activity in post-ribosomal supernatants of tobacco leaves. The tobacco activity is very stable at low temperatures, but quickly inactivated above 45 degrees C. It is relatively resistant to proteases and insensitive to -SH group reagents and to ionic conditions. It does not require, nor is it inhibited by, divalent cations. Although these properties are shared by the Escherichia coli beta-glucuronidase, the two activities can be distinguished by: (i) their different sensitivity to the specific inhibitor saccharic acid-1,4-lactone; (ii) their different thermal stability (iii) their different pH optima (5.0 for the plant activity and close to neutral for the bacterial enzyme). Therefore, under appropriate experimental conditions, it should be possible to assay the E. coli beta-glucuronidase in transgenic plants without interference from the endogenous plant activity.

One step purification of Escherichia coli beta-glucuronidase

beta-glucuronidase was purified by affinity chromatography on thiophenyl-glucuronide coupled to Sepharose. The enzyme was more than 95% pure. This enzyme is a tetramer composed of identical 74 kDa monomers. The amino-terminal sequence determined was: NH2-Met-Leu-Arg-Pro-Val.

Immunological specificity of beta-glucuronidase from human seminal plasma and its immunolocalization in the human reproductive tract

Beta-glucuronidase (beta-glucuronidase) in human seminal plasma consists of two forms of isozymes (major and minor forms). Antiserum prepared against the purified major form of beta-glucuronidase in rabbits was used for studies of immunological specificity and immunohistochemical localization of beta-glucuronidase in the human male reproductive tract. By ouchterlony immunodiffusion technique, anti-beta-glucuronidase serum showed reaction of identity with human tissue extracts such as liver, spleen, lungs, testis, epididymis, prostate, and seminal vesicles. Though monkey testis and epididymis extracts completely reacted with human seminal beta-glucuronidase antiserum, no cross-reaction was observed with mouse and rat tissue extracts. Immunofluorescent studies revealed that beta-glucuronidase is localized in the early stages of spermatogenesis in testis, in columnar cells of the epididymis, and in glandular cells of the prostate and seminal vesicles. Consistent absence of fluorescence in the lumens of testis and epididymis as well as negative cross-reaction between antiserum and sperm extracts suggested that major form of beta-glucuronidase in human seminal plasma is not immunologically identical with human spermatozoa. It is concluded that major form of beta-glucuronidase in seminal plasma is not tissue-specific although it appears to have limited species specificity.

Histochemical studies on genetical control of hormonal enzyme inducibility in the mouse. III. Beta-glucuronidase distribution pattern of epididymis in different genotypes

This article reports the application of Hayashi's histochemical technique for beta-glucuronidase to mouse epididymis. A methodological study, which established optimal conditions for demonstrating the enzyme in this organ, is reported. The distribution pattern of beta-glucuronidase is described and correlated with previous data for alpha-naphthyl acetate esterase. Differences between sites of granular and diffuse reaction product for these two enzymes are recorded. Possible interpretations of these findings in terms of intracellular localization of enzymes are discussed. Studies on different strains reveal regular differences in histochemical organization between mice of various genotypes. Histochemical data which imply androgen inducibility of beta-glucuronidase in mouse epididymis are preliminary noted.

Properties of two molecular forms of beta-glucuronidase from the mollusc Littorina littorea L

The occurrence of the two molecular forms, I and II, in the beta-glucuronidase of the liver (hepatopancreas) from the marine mollusc Littorina littorea L. has been demonstrated for the first time. The two forms have been purified 355-fold and 1262-fold, respectively. Form I and II of beta-glucuronidase behave differently on DEAE-cellulose chromatography, polyacrylamide gel disc electrophoresis, isoelectric focusing (pH 5.5 and 4.2, respectively), optimum pH (4.4 and 3.4--4.1, respectively), thermal stability, Km (1.2 mM and 0.5 mM with p-nitrophenyl beta-D-glucuronide, 0.3 mM and 0.15 mM with phenolphthalein beta-D-glucuronide as substrates for form I and II, respectively) and V. Their molecular weight, estimated by gel filtration through Sephadex G-200, was about 250000 for both forms. Several subunits were separated by polyacrylamide gel electrophoresis in presence of sodium dodecyl sulphate. This beta-glucuronidase is a glycoprotein, but sialic acid(s) were not detected. The enzyme was very active on synthetic substrates and also on hexasaccharides and tetrasaccharides containing glucuronic acid residues with beta 1 leads to 3 linkages; it had practially no activity on certain glycosaminoglycans. Hg2+ and glucaro-1,4-lactone were very effective inhibitors of this enzyme; the latter by a competitive mechanism.