Characterization of leaf and culm B-glucosidases of IR36 and brittle-stem rice (Oryza sativa) cultivars.

Date

3-1994

Degree

Bachelor of Science in Biology

Major Course

Major in Cell Biology

College

College of Arts and Sciences (CAS)

Adviser/Committee Chair

Evelyn Mae Tecson-Mendoza

Abstract

B-d-glucoside glucohydrolase (E.C. 3.2.1.21), was extracted from the leaf and culm of IR36 and brittle culm rice varieties at their grain filling stage. Two types of extracts from IR36 were obtained and characterized: cell-soluble (1S) and strongly ionically bound (SI). The specific activity (SA) of the enzyme was determined for all extracts from both plant parts of the IR36 and brittle culm rice plants. Optimum pH for enzyme reaction was 5 for all extracts. The enzyme was found to be stable at temperatures from 0-37 °C with the optimum temperature for enzyme reaction at 37 °C for both leaf extracts and 50 °C for both culm extracts. Michaelis constants and maximal velocities were determined with p-nitrophenyl-d-D-glucoside as substrate. Values for leaf Km were 1.7 and 2.2 mM for 1S and SI extracts, respectively while the Km of culm extracts were 0.72 and 0.51 mM for 1S and SI extracts, respectively. The Vmax of leaf extracts were 39 and 70 umol/hr/ml for 1S and SI extracts, respectively while for the culm extracts the Vmax values were 92 and 80 umol/hr/ml for 15 and SI extracts, respectively. The SA of the extracts were determined in terms of unit activity per milligram protein. Results showed that the SA of the culm extracts were higher than that of the leaves. This may reflect the need of the culm for B-glucosidase to catalyze lignification. Results also showed that the SA of the leaf extracts were not significantly different between varieties. The SA of the IR36 culm extracts were higher than that of the brittle-stem varieties, which may further confirm a relationship between 13-glucosidase activity and stem strength.

Language

English

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

Thesis

Document Type

Thesis

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