CHITINASE AND BETA-1,3-GLUCANASE IN THE LUTOID-BODY FRACTION OF HEVEALATEX

The lutoid-body (bottom) fraction of latex from the rubber tree (Hevea brasiliensis) contains a limited number of major proteins. These are, besides the chitin-binding protein hevein, its precursor and the C-te rminal fragment of this precursor, proteins with enzymic activities: t hree hevamine components, which are basic, vacuolar, chitinases with l ysozyme activity, and a beta-1,3-glucanase. Lutoid-body fractions from three rubber-tree clones differed in their contents of these enzyme p roteins. The hevamine components and glucanase were isolated and sever al enzymic and structural properties were investigated. These enzymes are basic proteins and cause coagulation of the negatively charged rub ber particles. The coagulation occurs in a rather narrow range of rati os of added protein to rubber particles, which indicates that charge n eutralization is the determining factor. Differences in coagulation of rubber particles by lutoid-body fractions from various rubber 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 rubber-tree clones with a high glucanase content in this fraction produce more latex than clones with little g lucanase. Sequence studies of two CNBr peptides of the glucanase indic ate that this protein is homologous with glucanases from other plants, and that a C-terminal peptide, possibly involved in vacuolar targetin g, may have been cleaved off. Copyright (C) 1996 Elsevier Science Ltd