Laccase from Aspergillus sp. (LC) was immobilized within Fe-BTC and ZIF-zni metal organic framewo... more Laccase from Aspergillus sp. (LC) was immobilized within Fe-BTC and ZIF-zni metal organic frameworks through a one-pot synthesis carried out under mild conditions (room temperature and aqueous solution). The Fe-BTC, ZIF-zni MOFs, and the LC@Fe-BTC, LC@ZIF-zni immobilized LC samples were characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The kinetic parameters (KM and Vmax) and the specific activity of the free and immobilized laccase were determined. Immobilized LCs resulted in a lower specific activity compared with that of the free LC (7.7 µmol min-1 mg-1). However, LC@ZIF-zni was almost 10 times more active than LC@Fe-BTC (1.32 µmol min-1 mg-1 vs 0.17 µmol min-1 mg-1) and only 5.8 times less active than free LC. The effect of enzyme loading showed that LC@Fe-BTC had an optimal loading of 45.2 mg g-1, at higher enzyme loadings the specific activity decreased. In contrast, the specific activity of LC@ZIF-zni increased linearly over the loading range investigated. The storage stability of LC@Fe-BTC was low with a significant decrease in activity after 5 days, while LC@ZIF retained up to 50% of its original activity after 30 days storage. The difference in activity and stability between LC@Fe-BTC and LC@ZIF-zni is likely due to release of Fe3+ and the low stability of Fe-BTC MOF. Together, these results indicate that ZIF-zni is a superior support for the immobilization of laccase.
In order to investigate the metabolism in vivo of homocystamine we needed the corresponding -SSO3... more In order to investigate the metabolism in vivo of homocystamine we needed the corresponding -SSO3H derivative and we attempted to prepare it. In this paper details are reported for the synthesis of S-(3-Aminopropyl)-thiosulfuric acid from 3-Bromopropylamine or thiosulfate. Same analytical date and chromatographic properties one also reported, which allow its identification.
Several Mediterranean shrubs, both autochthonous and naturalized, have been traditionally used as... more Several Mediterranean shrubs, both autochthonous and naturalized, have been traditionally used as food, flavouring and/or spicing agents, and as phytopharmaceuticals. The interest around 'natural' and 'biological' products is steadily increasing in developed countries. Therefore, it seems reasonable to screen some shrubs with regard to the actual information about their content of phytochemicals, in relation to both real and putative beneficial properties, and with particular concern to their 'antioxidant' power. Moreover, striking molecules from the examined shrubs are compared according to their occurrence in the various genera. Also, their structures and structure/activity relationship are discussed in the light of possible practical application.
... s: Laccase, Peroxidase, Polyphenol Oxidase, Assay, Psalliota. A. Rescigno*, E. Sanjust, L. Mo... more ... s: Laccase, Peroxidase, Polyphenol Oxidase, Assay, Psalliota. A. Rescigno*, E. Sanjust, L. Moatanam, F. Sollai, G. Soddu, AC Rinaldi, S. Oliva, A. Rinaldi Universita di Cagliari, Istituto di C hca Biologics, Via Pineta 77, Cagliari, ...
Melanin (eumelanin) is commonly produced in mammals starting from tyrosine and/or 3,4‐dioxyphenyl... more Melanin (eumelanin) is commonly produced in mammals starting from tyrosine and/or 3,4‐dioxyphenylalanine (DOPA) under the action of tyrosinase. 3‐Hydroxyanthranilic acid and 3‐hydroxykynurenine are intermediates occurring in the kynurenine pathway of tryptophan catabolism. In this paper, we show that these substances can interfere in melanin formation in vitro when tyrosine or DOPA is oxidized by molecular oxygen under catalysis by tyrosinase. In particular, when 3‐hydroxyanthranilic acid is present, a brown and apparently water‐soluble pigment is formed, whereas the typical eumelanin granules seem to become more and more rare as the concentration of 3‐hydroxyanthranilic acid increases. Also in the presence of the latter, the rate of tyrosine and/or DOPA consumption decreases. A very complicated 13C‐NMR spectrum indicates the high complexity of the reaction. This involves both the true melanin precursor(s) and the tryptophan metabolite, even if with peculiar mechanism and kinetics. When 3‐hydroxykynurenine is substituted for 3‐hydroxyanthranilic acid the reaction leads to reddish pigments whereas xanthommatins (the typical oxidation products of 3‐hydroxykynurenine) are absent. A possible relationship between some dischromic pathologies and tryptophan metabolic disorders is suggested.
Journal of Molecular Catalysis A-chemical, Jul 1, 2009
This paper describes the immobilization of the commercial synthetic tetrakis(pentafluorophenyl) p... more This paper describes the immobilization of the commercial synthetic tetrakis(pentafluorophenyl) porphine-iron(III) chloride on pyridyl-functionalized crosslinked poly(vinyl alcohol) and the catalytic activity of the adduct towards oxidation of selected organic substrates by hydrogen peroxide. The obtained adduct was characterized by UV/vis and IR spectroscopies. It showed a noticeable lignin-peroxidase-like catalytic activity; moreover a dramatic activity enhancement was observed in the presence
ABSTRACT 6-Hydroxydopa and 6-hydroxydopamine undergo autoxidation in the presence of molecular ox... more ABSTRACT 6-Hydroxydopa and 6-hydroxydopamine undergo autoxidation in the presence of molecular oxygen giving rise to the corresponding p-quinones. NAD(P)H:quinone oxidoreductase (QR) purified from Glycine max showed that it inhibited autoxidation of 6-hydroxydopa and 6-hydroxydopamine. The inhibition of autoxidation of 6-hydroxydopa was greater than 6-hydroxydopamine. QR had a potentiated effect in preventing 6-hydroxydopa oxidation in the presence of catalase and superoxide dismutase. Reduced glutathione increased protective effect when incubated with QR on both 6-hydroxydopa and 6-hydroxydopamine. Homogenized tissues from rat brain also showed to inhibit 6-hydroxydopa autoxidation. Our observations suggest a possible role for brain NAD(P)H:quinone oxidoreductase in protection of neurons from the toxic effect of quinones.
Ferula communis (L.), a plant belonging to Apiaceae, is widely present in Sardinia, Italy. Curren... more Ferula communis (L.), a plant belonging to Apiaceae, is widely present in Sardinia, Italy. Currently, interest in F. communis focuses on the presence of two chemotypes in the wild. One chemotype is poisonous to animals, whereas the other chemotype is non-poisonous. Polyphenol oxidase (PPO) has been extracted and partially purified from the two chemotypes of F. communis. The biochemical characterization of the enzymes showed significant differences. In particular, while the two PPOs were not able to use 6- and 7-hydroxycoumarin as substrates, they showed distinct specificity for 6,7- and 7,8-dihydroxycoumarin. Significant differences in the enzyme behavior towards common PPO inhibitors were also observed. In addition, activation energy and activation energy for denaturation were determined, showing significant differences between FP-PPO and FNP-PPO, particularly for denaturation kinetics. The possible roles of the two PPOs in determining differences in composition and toxicity of the two F. communis chemotypes are also discussed.
Laccase from Aspergillus sp. (LC) was immobilized within Fe-BTC and ZIF-zni metal organic framewo... more Laccase from Aspergillus sp. (LC) was immobilized within Fe-BTC and ZIF-zni metal organic frameworks through a one-pot synthesis carried out under mild conditions (room temperature and aqueous solution). The Fe-BTC, ZIF-zni MOFs, and the LC@Fe-BTC, LC@ZIF-zni immobilized LC samples were characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The kinetic parameters (KM and Vmax) and the specific activity of the free and immobilized laccase were determined. Immobilized LCs resulted in a lower specific activity compared with that of the free LC (7.7 µmol min-1 mg-1). However, LC@ZIF-zni was almost 10 times more active than LC@Fe-BTC (1.32 µmol min-1 mg-1 vs 0.17 µmol min-1 mg-1) and only 5.8 times less active than free LC. The effect of enzyme loading showed that LC@Fe-BTC had an optimal loading of 45.2 mg g-1, at higher enzyme loadings the specific activity decreased. In contrast, the specific activity of LC@ZIF-zni increased linearly over the loading range investigated. The storage stability of LC@Fe-BTC was low with a significant decrease in activity after 5 days, while LC@ZIF retained up to 50% of its original activity after 30 days storage. The difference in activity and stability between LC@Fe-BTC and LC@ZIF-zni is likely due to release of Fe3+ and the low stability of Fe-BTC MOF. Together, these results indicate that ZIF-zni is a superior support for the immobilization of laccase.
In order to investigate the metabolism in vivo of homocystamine we needed the corresponding -SSO3... more In order to investigate the metabolism in vivo of homocystamine we needed the corresponding -SSO3H derivative and we attempted to prepare it. In this paper details are reported for the synthesis of S-(3-Aminopropyl)-thiosulfuric acid from 3-Bromopropylamine or thiosulfate. Same analytical date and chromatographic properties one also reported, which allow its identification.
Several Mediterranean shrubs, both autochthonous and naturalized, have been traditionally used as... more Several Mediterranean shrubs, both autochthonous and naturalized, have been traditionally used as food, flavouring and/or spicing agents, and as phytopharmaceuticals. The interest around 'natural' and 'biological' products is steadily increasing in developed countries. Therefore, it seems reasonable to screen some shrubs with regard to the actual information about their content of phytochemicals, in relation to both real and putative beneficial properties, and with particular concern to their 'antioxidant' power. Moreover, striking molecules from the examined shrubs are compared according to their occurrence in the various genera. Also, their structures and structure/activity relationship are discussed in the light of possible practical application.
... s: Laccase, Peroxidase, Polyphenol Oxidase, Assay, Psalliota. A. Rescigno*, E. Sanjust, L. Mo... more ... s: Laccase, Peroxidase, Polyphenol Oxidase, Assay, Psalliota. A. Rescigno*, E. Sanjust, L. Moatanam, F. Sollai, G. Soddu, AC Rinaldi, S. Oliva, A. Rinaldi Universita di Cagliari, Istituto di C hca Biologics, Via Pineta 77, Cagliari, ...
Melanin (eumelanin) is commonly produced in mammals starting from tyrosine and/or 3,4‐dioxyphenyl... more Melanin (eumelanin) is commonly produced in mammals starting from tyrosine and/or 3,4‐dioxyphenylalanine (DOPA) under the action of tyrosinase. 3‐Hydroxyanthranilic acid and 3‐hydroxykynurenine are intermediates occurring in the kynurenine pathway of tryptophan catabolism. In this paper, we show that these substances can interfere in melanin formation in vitro when tyrosine or DOPA is oxidized by molecular oxygen under catalysis by tyrosinase. In particular, when 3‐hydroxyanthranilic acid is present, a brown and apparently water‐soluble pigment is formed, whereas the typical eumelanin granules seem to become more and more rare as the concentration of 3‐hydroxyanthranilic acid increases. Also in the presence of the latter, the rate of tyrosine and/or DOPA consumption decreases. A very complicated 13C‐NMR spectrum indicates the high complexity of the reaction. This involves both the true melanin precursor(s) and the tryptophan metabolite, even if with peculiar mechanism and kinetics. When 3‐hydroxykynurenine is substituted for 3‐hydroxyanthranilic acid the reaction leads to reddish pigments whereas xanthommatins (the typical oxidation products of 3‐hydroxykynurenine) are absent. A possible relationship between some dischromic pathologies and tryptophan metabolic disorders is suggested.
Journal of Molecular Catalysis A-chemical, Jul 1, 2009
This paper describes the immobilization of the commercial synthetic tetrakis(pentafluorophenyl) p... more This paper describes the immobilization of the commercial synthetic tetrakis(pentafluorophenyl) porphine-iron(III) chloride on pyridyl-functionalized crosslinked poly(vinyl alcohol) and the catalytic activity of the adduct towards oxidation of selected organic substrates by hydrogen peroxide. The obtained adduct was characterized by UV/vis and IR spectroscopies. It showed a noticeable lignin-peroxidase-like catalytic activity; moreover a dramatic activity enhancement was observed in the presence
ABSTRACT 6-Hydroxydopa and 6-hydroxydopamine undergo autoxidation in the presence of molecular ox... more ABSTRACT 6-Hydroxydopa and 6-hydroxydopamine undergo autoxidation in the presence of molecular oxygen giving rise to the corresponding p-quinones. NAD(P)H:quinone oxidoreductase (QR) purified from Glycine max showed that it inhibited autoxidation of 6-hydroxydopa and 6-hydroxydopamine. The inhibition of autoxidation of 6-hydroxydopa was greater than 6-hydroxydopamine. QR had a potentiated effect in preventing 6-hydroxydopa oxidation in the presence of catalase and superoxide dismutase. Reduced glutathione increased protective effect when incubated with QR on both 6-hydroxydopa and 6-hydroxydopamine. Homogenized tissues from rat brain also showed to inhibit 6-hydroxydopa autoxidation. Our observations suggest a possible role for brain NAD(P)H:quinone oxidoreductase in protection of neurons from the toxic effect of quinones.
Ferula communis (L.), a plant belonging to Apiaceae, is widely present in Sardinia, Italy. Curren... more Ferula communis (L.), a plant belonging to Apiaceae, is widely present in Sardinia, Italy. Currently, interest in F. communis focuses on the presence of two chemotypes in the wild. One chemotype is poisonous to animals, whereas the other chemotype is non-poisonous. Polyphenol oxidase (PPO) has been extracted and partially purified from the two chemotypes of F. communis. The biochemical characterization of the enzymes showed significant differences. In particular, while the two PPOs were not able to use 6- and 7-hydroxycoumarin as substrates, they showed distinct specificity for 6,7- and 7,8-dihydroxycoumarin. Significant differences in the enzyme behavior towards common PPO inhibitors were also observed. In addition, activation energy and activation energy for denaturation were determined, showing significant differences between FP-PPO and FNP-PPO, particularly for denaturation kinetics. The possible roles of the two PPOs in determining differences in composition and toxicity of the two F. communis chemotypes are also discussed.
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Papers by Enrico Sanjust