41 ACC合成酵素のリン酸化の生理的役割

抄録

ACC synthase(ACS), which is a key enzyme in the pathway of ethylene biosynthesis, is regulated transcriptionally. However, recent studies have raised the possibility that ACS is regulated not only transcilptionally but also post--translationally. We found that enzyme activities of some ACS isozymes in cell were regulated by phosphorylation. LE-ACS2, which is tomato wound-inducible isozyme, was phosphorylated on serine-460 residue by protein kinase in the presence of Ca^<2+>. We prepared the antibody that recognized the phosphorylation state of LE-ACS2 using the synthetic phosphorylated peptide as antigen. Western blot analyses using this antitbody revealed that LE-ACS2 was immediately phosphorylated flier translation. Next, analyses by in vitro phosphorylation system demonstrated that not only LE-ACS2 but also LE-ACS1A, 3, 6, VR-ACS6 were phosphorylated, whereas LE-ACS4 was not phosphorylated. That is, ACS isozymes that were induced by external stimuli, such as wounding, touch, and exogenous auxin, were phosphorylated, where. as ACS isozymes that were induced by intemal stimuli, such as ripening: developmentally (genetically) program though the plant life, were not phosphorylated, suggesting the physiological meaning.