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Biochemical characterization of a strictly specific beta‐galactosidase from the digestive juice of the palm weevil Rhynchophorus palmarum larvae
Author(s) -
YAPI Désiré Y. A.,
NIAMKE Sebastien L.,
KOUAME Lucien P.
Publication year - 2007
Publication title -
entomological science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.536
H-Index - 28
eISSN - 1479-8298
pISSN - 1343-8786
DOI - 10.1111/j.1479-8298.2007.00232.x
Subject(s) - size exclusion chromatography , gel electrophoresis , hydrolysis , chemistry , polyacrylamide gel electrophoresis , chromatography , galactose , lactose , biochemistry , sodium dodecyl sulfate , sodium , enzyme , organic chemistry
A beta‐galactosidase from the digestive juice of the palm weevil Rhynchophorus palmarum L. larvae was purified by chromatography on ion exchange, gel filtration, and hydrophobic interaction columns. The preparation was shown to be homogeneous on polyacrylamide gel. Beta‐galactosidase was a monomeric protein with a molecular weight of 62 kDa based on its mobility in sodium dodecyl sulfate–polyacrylamide gel electrophoresis and 60 kDa based on gel filtration. Maximal enzyme activity occurred at 55°C and pH 5.0. The purified beta‐galactosidase was stable at 37°C and its pH stability was in the range of 4.6–6.0. Beta‐galactosidase was highly specific for the beta‐ d ‐galactosyl residue and beta‐(1‐4) linkage. The catalytic efficiency (V max /K m ) values for p ‐nitrophenyl‐beta‐ d ‐galactopyranoside, beta‐ d ‐galactosyl(1‐4)‐ d ‐glucose (lactose), beta‐ d ‐galactosyl(1‐4)‐ d ‐galactose and beta‐ d ‐galactosyl(1‐4)‐beta‐ d ‐galactosyl(1‐4)‐ d ‐glucose were, respectively, 72.95, 10.97, 20.74 and 12.73. 5,5‐Dithio‐bis(2‐nitrobenzoate) and sodium dodecyl sulfate inhibited completely the beta‐galactosidase activity. The enzyme was capable of catalyzing transgalactosylation reactions. The yield of galactosylation of 2‐phenylethanol (43%), catalyzed by the beta‐galactosidase in the presence of lactose as galactosyl donor, is higher than those reported previously with conventional sources of beta‐galactosidases. In addition, the optimum pH is different for the hydrolysis (pH 5.0) and transgalactosylation reactions (pH 6.0).