Studies on maize beta glucosidase gene-enzyme system
| dc.contributor.author | Rifaat, Mahmoud M. | en |
| dc.contributor.committeechair | Esen, Asim | en |
| dc.contributor.committeemember | Bates, Robert C. | en |
| dc.contributor.committeemember | Falkinham, Joseph O. III | en |
| dc.contributor.committeemember | Johnson, John L. | en |
| dc.contributor.committeemember | Wallace, Bruce | en |
| dc.contributor.department | Genetics | en |
| dc.date.accessioned | 2015-06-24T13:35:20Z | en |
| dc.date.available | 2015-06-24T13:35:20Z | en |
| dc.date.issued | 1988 | en |
| dc.description.abstract | Maize ß-glucosidase is implicated in phytohormone catabolism, disease resistance mechanisms, and also the catabolism of various ß-D-glucosides. The enzyme expressed in maize sporophytes is encoded by a highly polymorphic locus, Glul (chromosome 10). In the present study, maize ß-glucosidase was purified to homogeneity by using differential solubility and chromatography. The enzyme is soluble and synthesized adaptively after germination. The isoelectric point (pl) of the native enzyme is 4.9-5.0 and its temperature and pH optima are 40°C and 6.8, respectively. The active enzyme is temperature·sensitive and composed of two identical, non-covalently associated and catalytically inactive polypeptides (60 kD each). Enzyme catalysis shows dominant aryl ß-glucosidase and ß-fucosidase activities compared to cellobiase activity. Activity is (1) influenced by the configuration of the C-4 and C-6 atoms on the glycone moeity and by the substrate chain length, (2) possibly mediated by an imidazole ring and a terminal α-amino group in the enzyme catalytic and binding sites, respectively, (3) dependent on intra-chain disulfide bonds to maintain the enzyme conformation, and (4) inhibited competitively by the end product, glucose. The sporophytic specificity of Glul expression might be controlled by tightly linked cis- and trans- acting regulatory elements. One of the several null mutations, with an apparent allelism to Glul locus, (l) complements in trans when combined with normal Glul alleles, and (2) probably affects a shift in the tissue-specific expression of Glul locus (from sporophytic to gametophytic). Another structural gene, GIu3, encoding a soluble, sporophyte-specific, and electrophoretically-invariant ß-glucosidase isoenzyme is present based on hydrodynamic properties, size, surface net charge, peptide map, quaternary structure, and enzyme kinetics. | en |
| dc.description.degree | Ph. D. | en |
| dc.format.extent | xi, 151 leaves | en |
| dc.format.mimetype | application/pdf | en |
| dc.identifier.uri | http://hdl.handle.net/10919/53601 | en |
| dc.language.iso | en_US | en |
| dc.publisher | Virginia Polytechnic Institute and State University | en |
| dc.relation.isformatof | OCLC# 18621096 | en |
| dc.rights | In Copyright | en |
| dc.rights.uri | http://rightsstatements.org/vocab/InC/1.0/ | en |
| dc.subject.lcc | LD5655.V856 1988.R532 | en |
| dc.subject.lcsh | Corn -- Genetics | en |
| dc.subject.lcsh | Enzymes -- Analysis | en |
| dc.title | Studies on maize beta glucosidase gene-enzyme system | en |
| dc.type | Dissertation | en |
| dc.type.dcmitype | Text | en |
| thesis.degree.discipline | Genetics | en |
| thesis.degree.grantor | Virginia Polytechnic Institute and State University | en |
| thesis.degree.level | doctoral | en |
| thesis.degree.name | Ph. D. | en |
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