SCREENING FOR LINAMARASE IN SOME YEAST STRAINS, AND CHARACTERIZATION OF LINAMARASE FROM DRIED CASSAVA (MANIHOT ESCULENTA) CORTEX.
SCREENING FOR LINAMARASE IN SOME YEAST STRAINS, AND CHARACTERIZATION OF LINAMARASE FROM DRIED CASSAVA (MANIHOT ESCULENTA) CORTEX.
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Date
1996-01
Authors
ONYIKE, ELEWECHI
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Abstract
Dried Cassava (Manihot esculenta) cortex contains
1inamarase with high activity. The 1inamarase was purified 97
fold by ammonium sulphate fractionation, and gel filtration on
Sephadex G-150. The enzyme has Km values of 0.75 and 2.22mM
with respect to the artificial substrate, p-nitropheny 1-B-Dglucoside,
and its natural substrate linamarin, respectively.
D-gluconolactone is a strong competitive inhibitor of the
enzyme with Ki of 0.22mM when p-nitopheny 1-B-D-glucoside is
the substrate. The pH optimum of the enzyme is 6.5. Analysis
of the effects of pH and temperature on 1inamarase activity
and kinetic constants indicates that the carboxyl group of
aspartate or glutamate and the imidazole of histidine may be
involved in the enzyme catalysis. Linamarase from cassava was
significantly inhibited by potassium cyanide and citric acid.
The enzyme was found to be stable up to 48°C and the optimum
temperature of the linamarase catalyzed hydrolysis was 36°C.
The energy of activation was found to be about 3.92 Kcal/mole.
The isolated enzyme was found to be very efficient in the
hydrolysis of bound cyanide in any of the cassava products,
' gari' and ' lafun' . A substantial quantity of cyanide, was
found in sour ' gari' which is generally considered as having
little or no cyanide in it.
Description
A thesis submitted to the Postgraduate School,
Ahmadu Bello University, Zaria, in Partial
fulfillment of the requirement for the degree of:
DOCTOR OF PHILOSOPHY IN BIOCHEMISTRY
DEPARTMENT OF BIOCHEMISTRY
FACULTY OF SCIENCE
AHMADU BELLO UNIVERSITY
ZARIA, NIGERIA
Keywords
SCREENING, LINAMARASE, YEAST, STRAINS, CHARACTERIZATION, LINAMARASE, DRIED, CASSAVA, MANIHOT, ESCULENTA, CORTEX