1,721,096 research outputs found
PLANT COPPER-AMINE OXIDASES
No full textIn this review, the widely distributed plant copper-amine oxidases are described. The purification procedures, molecular features, substrate specificities, inhibitors, the stoichiometry of the catalysed reaction, spectroscopic features, the prosthetic groups and reaction mechanisms, are all reviewed
Oxidation of benzylamine Br-derivatives by lentil seedling copper-amine oxidase
No full textCopper amine oxidase was shown to be able to catalyse the oxidative deamination of 2-, 3- and 4-Br-derivatives of benzylamine to the corresponding aldehydes, that all absorb at 250 nm. This change in the absorption spectrum made it possible to follow the enzyme reaction. 2-Br-benzylamine, 3-Br-benzylamine, and 4-Br-benzylamine showed K-m values similar to benzylamine, but 3-Br-benzylamine showed a slower k(C), which allows it to be a catalytically more efficient substrate. Under anaerobic conditions the native enzyme oxidised 1 equivalent of all Br-derivatives and released 1 equivalent of aldehyde per enzyme subunit. These findings demonstrate that, in anaerobic conditions, the enzyme can oxidise substrates with a single incomplete turnover. The possible involvement of the cofactor 6-hydroxydopa quinone and of a negatively charged residue in the oxidation of Br-benzylamines is discussed
Evaluation of antioxidant, anti-tyrosinase potentials and phytochemical composition of four Egyptian plants
No full textThe aim of this present research is to evaluate antioxidant and antityrosinase potentials and to investigate the phytoconstituents of methanol (70%) extract from four Egyptian plants, Solanum rantonnetii, Tilia cordata, Cichorium intybus (L.), and Lagerstroemia tomentosa. Antioxidant activity was measured by using two different free radical scavenging methods, 2,2'-Azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and 2,2-diphenyl-1-picrylhydrazyl radical (DPPH•), whereas polyphenols and flavonoids contents were evaluated by using Folin-Ciocalteau, and aluminum nitrate methods respectively. Tyrosinase inhibition was evaluated using commercial enzyme and dihydroxyphenylalanine (DOPA) as substrate and methanol extract of each plant was investigated by phytochemical analysis. The results showed that all the plants had good antioxidant activity where Cichorium intybus exhibited the highest antioxidant activity determined as total content of free-radical scavenging, polyphenol and flavonoid molecules, and showed the best tyrosinase inhibition activity compared with the other plants extracts studied. Chromatogarphic separation and NMR analysis of Cichorium intybus methanol extract revealed the identification of two coumarins, scopoletin and esculetin, and seven flavonoids, dihydroquercetin 7-4'-dimethyl ether, blumeatin, diosmetin, tamarixetin, quercetin, quercetin 3-O-β-galactoside and kaempferol 3-O-rutinoside. These findings suggest that Cichorium intybus is rich with bioactive compounds and could be used as a good source of potentially natural antioxidants and antityrosinase molecules
Purification and characterisation of a soluble nucleotide pyrophosphatase/phosphodiesterase from prickly pear (Opuntia ficus indica) fruits
No full textA glycosylated metallo-protein, nucleotide pyrophosphatase/phosphodiesterase, in a soluble form was purified to homogeneity from prickly pear (Opuntia ficus indica) fruits. The native protein had a molecular mass of 105 +/- 8 kDa and was formed by two apparently identical subunits each containing 1 Ca(2+) and 1 Mg(2+) ion. The Opuntia enzyme exhibited hydrolytic activities toward pyrophosphate/phosphodiester bonds of a broad range of natural substrates, but among these, only NAD(P) and NAD(P)H were hydrolysed very efficiently. Moreover, Opuntia pyrophosphatase/phosphodiesterase hydrolysed the artificial substrate thymidine 5'-monophosphate 4-nitrophenyl ester, whereas it did not show any catalytic activity toward bis-4-nitrophenyl phosphate, which is a substrate of other pyrophosphatase/phosphodiesterase enzymes. We observed an increase of enzyme activity from the green to the red stage of fruits development, suggesting that ONPP activity might be related to the ripening of prickly pears. The protein was shown to be resistant to 75 degrees C for 30 min. Other biochemical characteristics were investigated and are reported here
Oxidation of spermine by an amine oxidase from lentil seedlings
No full textSpermine is a substrate of lentil (Lens culinaris) seedling amine oxidase and the oxidation products are reversible inactivators of the enzyme. The spermine is oxidized at the terminal amino groups to a dialdehyde: 2 moles of hydrogen peroxide and 2 moles of ammonia per mole of spermine are formed. The pH optimum of the enzyme with spermine is 7.9 in Tl-HCl buffer; the K(m) value is 4.4. 10(-4) molar, similar to that found with other substrates (putrescine and spermidine)
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