INTRACELLULAR AND EXTRACELLULAR ISOFORMS OF PR-3 CLASS CHITINASE IN VIRUS-INFECTED CUCUMBER PLANTS

Cucumber (Cucumis sativus L. cv. Laura) contains three different isofo rms of chitinase (EC 3.2.1.14), thought to be involved in the defense against a pathogen. Using a highly specific rabbit antiserum raised ag ainst a predominant, extracellularly localized, virus-inducible acidic chitinase (p28), two additional enzyme isoforms with differential mod e of compartmentalization were identified. Immunoblot analysis of the fractionated plant extracts separated by denaturing and native (anodic and cathodic) polyacrylamide gel electrophoresis (PAGE) revealed that the chitinase p25 (M-r 25.5 K), is a basic, etxracellular isoform and the chitinase p24 (M-r 24.6 K) is an acidic, probably intracellular i soform of the enzyme.