- Lipase catalysed substituted coumarins with antioxidant activity
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Lipase has been employed as a green catalyst to esterify 7- and 6-hydroxy-4-methyl-coumarin with different fatty and acetic acid. The esterified coumarins have been evaluated for antioxidant activities using DPPH and ABTS assays, among them 3a and 5a are known as active antioxidants.
- Kidwai, Mazaahir,Poddar, Vaishali,Poddar, Roona
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p. 715 - 720
(2011/07/08)
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- Structure activity studies with xenobiotic substrates using carboxylesterases isolated from Arabidopsis thaliana
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Carboxylesterases (CXEs) catalyse the hydrolysis of xenobiotics and natural products radically altering their biological activities. Whereas the substrate selectivity of animal CXEs, such as porcine liver esterase (PLE) have been well studied, the respective enzymes in plants have yet to be defined and their activities determined. Using Arabidopsis thaliana (At) as a source, five representative members of the α/β hydrolase AtCXE family of proteins have been cloned, expressed and the purified recombinant proteins assayed for esterase activity with xenobiotic substrates. Two members, AtCXE5 and AtCXE18 were found to be active carboxylesterases, though AtCXE5 proved to be highly unstable as a soluble protein. AtCXE18 and the previously characterised S-formylglutathione hydrolase from Arabidopsis (AtSFGH) were assayed against a series of esters based on methylumbelliferone in which the acyl moiety was varied with respect to size and conformation. The same series was used to assay crude esterase preparation from Arabidopsis plants and the results compared with those obtained with the commonly used PLE. With straight chain esters, AtCXE18 behaved like PLE, but the Arabidopsis hydrolases proved less tolerant of branched chain acyl components than the mammalian enzyme. While none of the enzyme preparations accurately reflected all the activities determined with crude Arabidopsis protein extracts, the plant enzymes proved more useful than PLE in predicting the hydrolysis of the more sterically constrained esters.
- Cummins, Ian,Landrum, Marie,Steel, Patrick G.,Edwards, Robert
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p. 811 - 818
(2008/03/13)
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- A high-throughput, low-volume enzyme assay on solid support
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A high-throughput enzyme assay is described that uses 1 μL or less of enzyme solution for each test Enzyme solutions are deposited by robotic handling in a throughput of over 1000 tests/h on the surface of silica gel plates that have been preimpregnated with fluorogenic substrates. The reaction is quantitated by fluorescence. The method is compatible with water-insoluble substrates (lipases), water-soluble substrates (glycosidases), whole-protein substrates (proteases), and enzyme inhibition measurements. Hydrolytically labile umbelliferyl esters can be used to assay lipases in this format without background hydrolysis. High throughput and reproducibility were tested by fingerprint analysis of lipases and esterases against 37 different fluorogenic ester substrates. A set of eight fluorogenic unbelliferyl esters was selected for optimal activity screening of lipases and esterases on silica gel plates.
- Babiak, Peter,Reymond, Jean-Louis
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p. 373 - 377
(2007/10/03)
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- Method for the immediate identification of salmonella cultures
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The invention concerns a method for identifying immediately Salmonellae and distinguishing them from other bacteria by employing a reagent consisting of a 4-methylumbelliferone ester of an acid with 7-10 carbon atoms and a process for preparing said reagent.
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