B-Galactosidase from Coffea arabica and its role in fruit ripening
B-Galactosidase (EC 3.2.1.23) from ripe coffee berries was purified and characterized. The enzyme displayed activity against p-nitrophenil-B-D-galactopyranoside (PNPG) (Km 0.33 mM), lactose (Km 40 mM), arabinogalactan and galactan. Purification was carried out using (NH subíndice 4) subíndice 2SO subíndice 4 precipitation, gel-filtration using Bio-Gel P-2 and P-200, ion-exchange chromatography on Cellex-CM and affinity chromatography on p-aminophenil-B-D-thiogalactopyranoside-agarose. Activity was highest within a pH range of 2.5-6, with an optimum at pH 4.4 The M, was estimated to be 2.9 x 10 exponente 4 by SDS-PAGE. The enzyme appeared to be a dimer of two identical subunits. It was inhibited by galactose (competitive, K subíndice i 0.26 mM); p-chloromercuribenzoate (PCMB) at 0.29 mM completely abolished activity. The enzyme catalysed release of galactose from galactan and arabinogalactan; pectin yielded galactose only when the action of B- galactosidase was combined with that of an endopolygalacturonase from Aspergillus niger. B-Galactosidase activity in coffee berries showed a progressive increase of more than four-fold as the fruit developed from the immature to ripe stage, with a slight decrease in fully ripe fruit. The same trend was observed with three other glycosidases, but not for N-acetyl glucosaminidase. It is suggested that B-galactosidase plays a role in cell wall degradation such as occurs during fruit ripening.
| Main Authors: | , , |
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| Format: | biblioteca |
| Published: |
1993
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| Subjects: | COFFEA ARABICA, FRUTO, MADURAMIENTO, BETA GALACTOSIDASA, ENGIMAS, PECTINAS, |
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| Summary: | B-Galactosidase (EC 3.2.1.23) from ripe coffee berries was purified and characterized. The enzyme displayed activity against p-nitrophenil-B-D-galactopyranoside (PNPG) (Km 0.33 mM), lactose (Km 40 mM), arabinogalactan and galactan. Purification was carried out using (NH subíndice 4) subíndice 2SO subíndice 4 precipitation, gel-filtration using Bio-Gel P-2 and P-200, ion-exchange chromatography on Cellex-CM and affinity chromatography on p-aminophenil-B-D-thiogalactopyranoside-agarose. Activity was highest within a pH range of 2.5-6, with an optimum at pH 4.4 The M, was estimated to be 2.9 x 10 exponente 4 by SDS-PAGE. The enzyme appeared to be a dimer of two identical subunits. It was inhibited by galactose (competitive, K subíndice i 0.26 mM); p-chloromercuribenzoate (PCMB) at 0.29 mM completely abolished activity. The enzyme catalysed release of galactose from galactan and arabinogalactan; pectin yielded galactose only when the action of B- galactosidase was combined with that of an endopolygalacturonase from Aspergillus niger. B-Galactosidase activity in coffee berries showed a progressive increase of more than four-fold as the fruit developed from the immature to ripe stage, with a slight decrease in fully ripe fruit. The same trend was observed with three other glycosidases, but not for N-acetyl glucosaminidase. It is suggested that B-galactosidase plays a role in cell wall degradation such as occurs during fruit ripening. |
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