Comparison of linamarase from different tissues of cassava
1992
Phannee Sawangareetrakul | Jisnuson Svasti (Mahidol Univ., Bangkok (Thailand). Faculty of Science. Dept. of Biochemistry)
Linamarase, a Beta-glycosidase enzyme catalysing the hydrolysis of cyanogenic glucosides, was purified from different tissues of the cassava, namely petiole, stem and root cortex. The procedure involved extraction, treatment with PVPP and Dowex 2 X-8, ammonium sulphate fractionation and Sepharose 4B Chromatography. The high molecular weight material (600-2,000 kd) contained high levels of Beta-glucosidase and Beta-fucosidase activity and low amounts of Beta-galactosidase activity. In addition, small amounts of Beta-galactosidase activity were found in the lower molecular material. On SDS-polyacrylamide gel electrophoresis, the high MW peak from Sepharose gave a single band of Mr 63 kd, while the low MW peak gave several bands, none of which was of 63 kd. This suggests that in addition to linamarase present in the high MW peak, cassava tissues also contain a low MW Beta-galactosidase present in small amounts and still impure. Analysis of hexose and sialic acid content of the high MW linamarase showed that stem and petiole enzymes had a similar content of hexose and sialic acid, but the root cortex enzyme had higher contents of both components. Tryptic peptide mapping of linamarase by paper electrophoresis showed similarities between enzymes from all three tissues, but each tissue also showed 1-2 distinctive peptides. Further structural analysis of these peptides will be required to determine whether these peptide differences are due to differences in amino acid sequence or due to differences in the extent of glycosylation.
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