Physiologia plantarum vol:104 issue:2 pages:175-182
Six chitinases (EC 18.104.22.168) were purified from salicylate-treated leek (Allium porrum L.). They all strongly bind to chitin and can roughly be divided into two groups. One group has blocked W-termini, is completely inhibited by 1 mM AgNO3, has a relatively narrow pH optimum, a temperature optimum of 40 degrees C and cannot degrade the tetramer of chitin. The other group has unblocked N-termini showing homology to the chitin-binding lectin WGA and is therefore considered as class I chitinases. This group is only moderately inhibited by 1 mM AgNO3 (30%), has a relatively broad pH optimum, has a higher temperature optimum (50 to 60 degrees C) and can degrade the tetramer of chitin to dimers. Furthermore, all isoforms have molecular masses around 34 kDa as estimated by SDS-PAGE. They have isoelectric points ranging From 4 to 8 and no detectable lysozyme activity. Two isoforms investigated in more detail differ in their antifungal potential.