M. Elias et al., CHARACTERIZATION OF LINAMARASE OF LATEX AND ITS LOCALIZATION IN PETIOLES IN CASSAVA, Archives of biochemistry and biophysics, 341(2), 1997, pp. 222-228
The distribution of linamarase in latex and its purification, characte
rization, and immunocytochemical localization in petioles were studied
in order to get an insight into the process of cyanogenesis in cassav
a. Crude latex exudate exhibited low linamarase activity, but on dilut
ion the activity increased about fivefold. Assay using petiole latex c
ollected in isotonic medium showed that the enzyme was distributed in
vesicle-like structures. In vitro studies showed that about 50% activi
ty was released from the vesicle into the medium within an hour. Latex
linamarase was purified by ammonium sulfate fractionation and DEAE-ce
llulose chromatography and was characterized with respect to its amino
acid composition and kinetic properties. Gel filtration and SDS-PAGE
analysis showed that the enzyme was made up of a 70,000-Da peptide. Im
munocytochemical studies on the localization of linamarase in cassava
petioles showed sporadic positive staining in the phloem and intense s
taining in the thickened corners of the collenchyma cells of the corte
x, suggesting the distribution of linamarase in laticifers as well as
in the cell wall. (C) 1997 Academic Press.