Isoforms of Linamarase in Cassava (Manihot esculenta)

Abstract

Linamarase (EC. 3.2.1.21) was purified from different tissues of cassava (leaf, rind and tuber) to compare the kinetic properties and characteristics of the enzyme in these tissues. Purified enzyme preparation appeared as single band of average molecular size 70 kD in SDS-PAGE gels. The kinetic properties of linamarase with respect to pH and temperature indicated that tuber linamarase possessed a broader pH optimum and higher temperature stability as compared to leaf and rind enzymes. Differences in Km values for linamarin were observed with leaf linamarase having the highest Km value (500 μM) followed by rind (400 μM) and then tuber (250 μM) linamarases. Rind enzyme appeared to be less susceptible to urea denaturation than the leaf enzyme. Comparison of elution profiles from DEAE-Cellulose indicated that the relative amounts of the various ionic forms of the enzyme differed in the case of each tissue. Elution patterns of the enzyme from Con A-Sepharose also differed, suggesting difference in glycosylation among leaf, rind and tuber enzymes. This was confirmed by carbohydrate analysis which showed that the tuber linamarase contained significantly higher amount of protein bound carbohydrate. These results suggest the possible occurrence of different forms of linamarase in cassava.