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Evidence for beta-galactosidase catalyzed hydrolysis of paranitrophenyl-beta-D-galactopyranoside anchored in cyclodextrins.
Jyothirmayi, N. and Ramadoss, C. S. (1993) Evidence for beta-galactosidase catalyzed hydrolysis of paranitrophenyl-beta-D-galactopyranoside anchored in cyclodextrins. Indian Journal of Biochemistry & Biophysics, 30 (4). pp. 218-23. ISSN 0301-1208
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Ind Jl. of Biochem & Biophy 1993 218.pdf - Published Version Restricted to Registered users only Download (1MB) | Request a copy |
Abstract
The absorption maximum of p-nitrophenol upon mixing with molar equivalents of alpha-cyclodextrin (alpha-CD) or hydroxypropyl-beta-cyclodextrin (HPB) showed nearly 5 nm shift to the longer wavelength region, indicative of complex formation, while beta-cyclodextrin (beta-CD), gamma-cyclodextrin (gamma-CD) and hydroxyethyl-beta-cyclodextrin (HEB) produced only a marginal shift of about 1-2 nm, suggestive of a weaker interaction. It has been shown by circular dichroism spectral studies that the aglycon part of p-nitrophenyl-beta-D-glycoside (PNPG) is also encapsulated by alpha-cyclodextrin. The encapsulated form of PNPG could be hydrolyzed by beta-galactosidase, the temperature and pH-optima for hydrolysis of anchored substrates being essentially identical to that of free substrate. However, small but consistent increase in Km values were obtained for alpha-cyclodextrin-, HEB- and HPB-anchored substrates. The kcat values also registered an increase for the HEB- and HPB-anchored substrates. However, there was no increase in kinetic efficiency (kcat/Km) of enzyme. The inhibition noted at higher concentrations of HEB- and gamma-cyclodextrin-anchored PNPG but not with o-nitrophenyl-beta-D-galactoside (ONPG)-cyclodextrin mixture suggests that PNPG-cyclodextrin complexes were responsible for the inhibition. Taken together, these results suggest that the enzyme catalyses the hydrolysis of anchored substrates.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | cyclodextrin, beta galactosidase, hydrolysis |
| Subjects: | 500 Natural Sciences and Mathematics > 04 Chemistry and Allied Sciences > 28 Polysaccharide Chemistry |
| Divisions: | Dept. of Biochemistry |
| Depositing User: | Food Sci. & Technol. Information Services |
| Date Deposited: | 15 Nov 2021 04:21 |
| Last Modified: | 15 Nov 2021 04:21 |
| URI: | http://ir.cftri.res.in/id/eprint/2285 |
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