BIOCHEMICAL AND MOLECULAR STUDIES ON β-GLYCOSIDASE FROM SORGHUM (Sorghum bicolor (L) Moench) AND CASSAVA (Manihot esculenta Crantz)

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dc.contributor.authorADOBE, KWANASHIE
dc.date.accessioned2014-02-14T11:03:50Z
dc.date.available2014-02-14T11:03:50Z
dc.date.issued2012-12
dc.descriptionA THESIS REPORT SUBMITTED TO THE POSTGRADUATE SCHOOL, AHMADU BELLO UNIVERSITY, ZARIA IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE MASTER OF SCIENCE DEGREE IN BIOCHEMISTRY (M Sc. BIOCHEMISTRY) DEPARTMENT OF BIOCHEMISTRY FACULTY OF SCIENCE AHMADU BELLO UNIVERSITY ZARIA, NIGERIA. DECEMBER, 2012en_US
dc.description.abstractGenes encoding linamarase from cassava root cortex and dhurrinase from sorghum seeds were amplified using the polymerase chain reaction. Crude extracts of linamarase and dhurrinase containing most of the intracellular proteins were used to hydrolyze pnitrophenyl-β-D-glucopyranoside (pNP) and linamarin extracted from cassava cortex. A gene fragment corresponding to linamarase (1,504 bp) was amplified. The native enzyme showed an optimum pH of 6.0 for pNP hydrolysis. The optimum temperature observed from the experimental assay showed that cassava linamarase has maximum activity for the hydrolysis of pNP at 65°C. The Q10, calculated between 40°C and 50°C was 1.17. Activation energy (Ea) was found to be 17.32 KJ/mol (4.14 kcal mol-1). The KM for linamarase was 5.75 x 10-3 µmol l-1 with a kcat value of 3.41 min-1 and Vmax of 1.96 x 10 -2 µmol l-1 min-1. A 1,695 bp fragment corresponding to dhurrinase gene was also amplified. Dhurrinase enzyme activity was stable at room temperature (25oC) with optimum temperature of 65oC. Temperature coefficient (Q10) calculated between 40oC and 50oC gave a value of 2.53. Activation energy (Ea) of 51.06 KJ/mol was also extrapolated. The pH activity curve put maximal activity for dhurrinase at pH 5.0. The double reciprocal plot of dhurrinase showed a calculated KM of 1.39 x 10-2 µmol l-1, Vmax of 1.01 x 10-1 µmol l-1 min-1 and kcat of 7.27 min-1. Initial velocity data clearly showed that dhurrinase had an index of physiological efficiency (kcat) of 7.27 min-1. Half life of enzyme activity (using linamarin as substrate) extrapolated from steady state data favored dhurrinase (288.79 min), linamarase showing a half life of 117.47 min. Our investigations have shown clearly that dhurrinase holds the capacity to totally detoxify cassava and its products of cyanogenic principles more effectively than linamarase.en_US
dc.identifier.urihttp://hdl.handle.net/123456789/1551
dc.language.isoenen_US
dc.subjectBIOCHEMICAL,en_US
dc.subjectMOLECULAR,en_US
dc.subjectSTUDIES,en_US
dc.subjectβ-GLYCOSIDASE,en_US
dc.subjectSORGHUM,en_US
dc.subjectSorghum,en_US
dc.subjectbicolor,en_US
dc.subjectMoench,en_US
dc.subjectCASSAVA,en_US
dc.subjectManihot,en_US
dc.subjectesculenta,en_US
dc.subjectCrantz,en_US
dc.titleBIOCHEMICAL AND MOLECULAR STUDIES ON β-GLYCOSIDASE FROM SORGHUM (Sorghum bicolor (L) Moench) AND CASSAVA (Manihot esculenta Crantz)en_US
dc.typeThesisen_US
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