Source Year: 1997

The lutoid-body fraction of latex from Hevea brasiliensis contains a limited number of major proteins (hevein, its precursor and the C-terminal fragment of this precursor, proteins with enzymic activities : 3 hevamine components, which are basic, vacuolar, chitinases with lysozyme activity, and a B-1,3-glucanase). Lutoid-body fractions from 3 clones (GT 1, PR 261 and LCB 1320) differed in their contents of these proteins. The hevamine components and glucanase were isolated and several enzymic and structural properties were investigated. These enzymes are basic proteins that cause coagulation of the negatively charged rubber particles. The coagulation occures in a rather narrow range of ratios of added protein to rubber particles, which indicates that charge neutralization is the determining factor. Differences in coagulation of rubber particles by lutoid-body fractions from different clones can be explained by their content of hevamine and glucanase. Glucanase from the lutoid-body fraction may dissolve callus tissue and this may explain the observation that clones with a high glucanase content produce more latex than clones with little glucanase. Sequence studies of 2CNBr peptides of the glucanase indicate that this protein is homologous with glucanase from other plants, and that a C-terminal peptide, possibly involved in vacuolar targeting, may have been cleaved off.