STUDIES ON CASSAVA MANIHOT UTILISSIMA POHL - .I. CYANOGENESIS - BIOSYNTHESIS OF LINAMARIN AND LOTAUSTRALIN IN ETIOLATED SEEDLINGS

No HCN could be detected in seeds of one cultivar of Manihot utilissima Pohl whereas seeds of two other cultivars contained 5·2-8·5 μg HCN/g fresh weight. However, 10-14-day-old seedlings of all three cultivars contained 156-260 μg HCN/g fresh weight. Thus a rapid biosynthesis of cyanogenic material occurred during germination. Chromatographic analysis showed that linamarin, 2(β-d-glucopyranosyloxy) isobutyronitrile, accounted for 93 per cent, while lotaustralin, 2(β-d-glucopyranosyloxy) 2-methylbutyronitrile, accounted for 7 per cent of the total HCN evolved by autolysing etiolated seedlings. l-Valine14C (U) and l-isoleucine14C (U) were incorporated by etiolated seedlings into the aglycone moieties of linamarin and lotaustralin respectively, indicating that the amino acids are effective precursors of these glucosides in M. utilissima. Seedlings of all three cultivars contained linamarase, the β-glucosidase which catalyses the hydrolysis of both glucosides. A crude preparation of the enzyme from leaves showed strong activity against linamarin and lotaustralin, mild activity against salicin, and weak activity against β-methyl glucoside and amygdalin. © 1970.