CAT and hyperinsulinemic hypoglycemia, familial, 4: In this regard, H2O2 is recognized as a key signaling molecule [83] and, under K+ deficiency, a general increase of the most relevant antioxidant systems that control H2O2 cellular content such as catalase, located in peroxisomes [84], and all the enzymes of the ascorbate-glutathione cycle in leaves and roots of C. maritima plants was observed.