Reporter glucuronidase

The same workers found the corresponding L-iduronic acid congener (87) to be a moderate inhibitor of )3-glucuronidase from human liver (K 1.3 pmol/1). The sodium salt of glucaro- lactam and strucural analogues thereof were recently reported to be potent inhibitors of pulmonary metastases and tumour cell invasion [138]. 

The involvement of testosterone in the testicular atrophy caused by di(2-ethyl-hexyl) phthalate was examined by co-administration of testosterone (1 mg/kg bw) subcutaneously with 2000 mg/kg bw di(2-ethylhexyl) phthalate [purity not specified] in groundnut oil to adult male Wistar rats for 15 days (Parmar et al., 1987). Administration of di(2-ethylhexyl) phthalate reduced the sperm count and also significantly increased the activity of y-GT, lactate dehydrogenase and P-glucuronidase and decreased the activity of sorbitol dehydrogenase and acid phosphatase. Co-adminis-tration of testosterone seemed to normalize the sperm count and the activity of testicular enz5mies. The role of testosterone in the testicular toxicity of di(2-ethylhexyl) phthalate has not been fully elucidated. Several reports refer to increased or decreased testosterone levels in plasma and testicular tissue. 

One of the main flavonols studied is quercetin. Indirect evidence for the presence of quercetin conjugates in humans was obtained by Manach et al [73], who found the presence of quercetin in plasma after the consumption of a complex meal rich in plant products only after P-glucuronidase and sulfatase treatment. Furthermore, the authors reported... 

The enzymatic hydrolysis is the method of choice when undesired reactions are to be avoided. /Tglucosidases (or /J-glucuronidases) from Helix pomatia digestive juice are now commercially available. They usually show a good hydrolytic performance, even if sometimes need long time reactions (days). Other enzymes are reported to have been used to specifically hydrolize saccharidic bonds like hesperidinase, /J-xylosidase, j3-galactosidase, and mixed crude enzymes like cellulase. 

Coumarins also have a C6-C3 skeleton, but they possess an oxygen heterocycle as part of the C3-unit. There are numerous coumarins, many of which play a role in disease and pest resistance, as well as UV-tolerance. The coumarin umbelliferone (1.21) is popular in enzyme assays. Umbelliferone esters can be used as a substrate for non-specific esterase enzyme assays and in fluorescent immunoassays (Jacks and Kircher, 1967). In order to quantify the enzyme activity of the popular reporter gene P-glucuronidase (GUS), plant extracts can be incubated with 4-methylumbelliferyl P-D-glucuronide (4-MUG 1.22), which upon hydrolysis... 

The earliest reports of the decomposition of /3-glucuronides by plant14 and mammalian16 preparations appeared in 1904 and 1908, respectively. It was not until 1934, however, that the systematic study of /3-glucuronidase commenced, with the characterization of the enzyme in ox kidney by Masamune.16... 

Glucuronidase from mammalian and non-mammalian sources, including the purified enzyme from female-rat preputial gland, often displays marked inhibition in the presence of excess substrate. The number of substrate molecules per active-enzyme center in the inactive enzyme-substrate complex ig24.100. ice.167 usuaUy 2, but values of166 3 and143 4 have also been reported. 

It seems feasible that traces of heavy-metal ions may have some bearing upon certain features of the action of mammalian /3-glucuronidase, such as the fall in net activity seen on dilution of highly purified preparations (see Section IV), the inhibitory action of the unknown constituents of urine,185 190 and the pH optimum at pH 3.4 observed by Mills, Paul, and Smith166 but by no other workers (see Section VI). The presence of traces of Cu in the assay mixture would provide a completely satisfactory explanation of the variable effects reported with L-ascorbic acid (see Section IX, 2).196s... 

Two further points of interest with regard to the specificity of /3-glu-curonidase are raised by recent reports that leech hyaluronidase is a poly-/ -glucuronidase,211 and that hydrolysis of certain mucopolysaccharides yielded some L-iduronic acid212 oligosaccharides containing this uronic acid resisted hydrolysis by /3-glucuronidase.209... 

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