Tomato root peroxidase isoenzymes: kinetic studies of the coniferylalcohol peroxidase activity, immunological properties and role in responseto salt stress

摘要

More than eleven soluble and ionically-bound cell wall peroxidase (EC 1.11.1.7; donor: hydrogen-peroxidase oxido-reductase) isoenzymes were found in tomato (Lycopersicon esculentum (L.) Mill. cv. Pera) roots. Isoperoxidases with isoelectric points 9.6, 8.2, 7.5, 6.5, and 3.6, were partially purified by ammonium sulfate precipitation, gel filtration on Sephacryl-S200 and ion exchange chromatography on DEAE Sephacel and/or SP-Sephadex C50 columns. Isoenzymes of pl 9.6, 3.6, and 6.5 showed the highest catalytic efficiencies with coniferyl alcohol, a true monolignol, used as substrate marker of peroxidases presumably involved in lignification. In addition, they showed cross-reactivity in Western blots of crude extracts when antibodies anti pl 3.6 isoenzyme were used for the immunodetection, despite their different pl values. It was demonstrated that the levels of pl 3.6 isoenzyme increased with the time of growth but did not respond to salt stress, unlike the isoenzyme with pl 9.6, which did. Thus, the expression of peroxidase isoenzymes involved in lignification may be differentially controlled by either developemental or stress signals.