Characterization of B- Glucosidases in IR36 and brittle culm mutant rice cultivars at various growth stages

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 T. Mendoza

Co-adviser

Joseph R. Bongon

Abstract

(β-D-glucoside glucohydrolase, (E.C. 3.2.1.211, was extracted for the first time from the culm and leaf sheaths of IR36 and brittle culm (bc) rice varieties to determine the unit activity, protein content and specific activity of the enzyme at different developmental stages. Soluble (1S) and strongly ionically bound (IB) enzyme extracts from IR36 were also characterized. Native PAGE was employed for isozyme detection at the seedling stage. Michaelis constants and maximal velocities determined for p-nitropheno1-11-D-glucoside were 0.517mM and 10.167 μmol/min/ml for soluble extract and 0.406mM and 2.375 μmol/min/ml for ionically bound extract. Optimum pH and temperature for enzyme reaction was at 5.0 and 50°C respectively and thermostability is within 4°C to 37°C. Optimum catalytic activity was retained for more than one month at 4°C. Native PAGE revealed the same banding patterns for all rice varieties. There were five isozymes observed from the 1S enzyme extract (Rf1 =0.015, Rf2 =0.03, Rf3 =0.045, Rf4 =0.09 and Rf5 =0.16) and two isozymes for the IB extract (Rf1 =0.015 and Rf2 = .0821. The slow-migrating bands observed indicate that the 11-glucosidase isozymes are of high MW. Specific activities (unit activity/mg protein) of both 15 and IB 13-glucosidase extracts from IR36 showed maximum activity at the grain-filling stage. This may be in response to the plant's need to increase lignin in its culm as the load of the plant increases. The be-1 variety, on the otherhand, exhibited lower activity at later stages of development which may explain the variety's poor resistance to lodging. No significant trends in activity at various stages of development of be-2 and be-3 varieties in both 1S and IB enzymes were observed.

Language

English

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

Thesis

Document Type

Thesis

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