Studies on Lipid Peroxides and the Enzymes Which Are Involved in Their Production in Taro Tubers Infected by Ceratocystis fimbriata

Hironori MASUI, Mioko NAKAYAMA, Masaru OHTURU
1993 Japanese Journal of Phytopathology  
Two enzymes, Lipoxygenase (LOX) and lipid hydroperoxide converting enzyme (LHCE), which are responsible for the production of antifungal lipid peroxides, were detected in taro tubers infected by Ceratocystis fimbriata. The infected taro tubers contained two LOX isozymes (LOX-1, LOX-2). The main isozyme of LOX was LOX-2 that showed optimal activity at pH 5.5. The enzyme (LOX-2) showed similar magnitude of activity toward linoleic acid (100%) and linolenic acid (77%), but did not show any
more » ... toward methyl linoleate (0%). It changed linoleic acid into 9-(9-LOOH) and 13-linoleate hydro peroxides (13-LOOH) in the ratio of 47: 53. The infected taro tubers contained two iso zymes of LHCE (LHCE-1, LHCE-2) with similar substrate specificity. When 9-or 13-LOOH of linoleic acid was used as the substrate of LHCE, main product was 9-or 13-hydroxyoctadecadienoic acid (LOH), respectively. 9, 12, 13-trihydroxyoctadecenoic acid (9, 12, 13 LOH) was produced as a minor product from 9-LOOH by LHCE. All of 9-and 13-LOOH, 9-and 13-LOH, and 9, 12, 13-LOH showed the similar toxicity toward both sweet potato and taro strains of C. fimbriata. On the other hand, the crude enzyme preparation (containing both LOX and LHCE) from the infected taro tubers converted linolenic acid into the peroxides compound(s), which inhibited the growth of sweet potato strain more severely than that of taro strain. (
doi:10.3186/jjphytopath.59.635 fatcat:sjfjhhcahbemlipsamp3xd5sta