Anti L-Ascorbate Peroxidase 1, Cytosolic (AP/AtAPx01) pAb (Rabbit, Ammonium Sulfate Purified)

Because plants have a sessile lifestyle, they must adjust to numerous external stimuli and coordinate their growth and development accordingly. The plant hormones, a group of structurally unrelated small molecules, are central to the integration of diverse environmental cues with a plant’s genetic program. The ‘classical’ phytohormones, identified during the first half of the twentieth century, are auxin, abscisic acid, cytokinin, gibberellin and ethylene. More recently, several additional compounds have been recognized as hormones, including brassinosteroids, jasmonate, salicylic acid, nitric oxide and strigolactones. Plants also use several peptide hormones to regulate various growth responses, but this class of hormones is beyond our scope here. With the application of genetic approaches, mainly in Arabidopsis thaliana, many aspects of hormone biology have been elucidated. Most hormones are involved in many different processes throughout plant growth and development. This complexity is reflected by the contributions of hormone synthesis, transport and signaling pathways, as well as by the diversity of interactions among hormones to control growth responses.

Genetic screens resulted in the identification of many of the proteins involved in hormone signaling and the analysis of these proteins has contributed significantly to our current models of hormone action. One particularly exciting outcome is the recent identification of receptors for auxin, gibberellin, jasmonate and abscisic acid. Though far from complete, our improved understanding of hormone perception and signaling has allowed for comparisons between hormones. From these it is clear that some hormones (cytokinins, ethylene and the brassinosteroids) use well-characterized signaling mechanisms. On the other hand, the identification and characterization of the auxin and jasmonate receptors, as well as proteins in gibberellin signaling, have highlighted a novel mechanism for hormone perception in which the ubiquitin–proteasome pathway has a central role. [from: Santner A., Mark E., Recent advances and emerging trends in plant hormone signalling (2009) Nature 459: 1071-1078]

Ascorbate peroxidase (or APX) is a member of the family of heme-containing peroxidases. Ascorbate-dependent peroxidase activity was first reported in 1979, more than 150 years after the first observation of peroxidase activity in horseradish plants and almost 40 years after the discovery of the closely related cytochrome c peroxidase enzyme. Peroxidases have been classified into three types (class I, class II and class III). Ascorbate peroxidase is a class I peroxidase enzyme. APXs catalyse the H2O2-dependent oxidation of ascorbate in plants, algae and certain cyanobacteria. APX has high sequence identity to cytochrome c peroxidase, which is also a class I peroxidase enzyme. Under physiological conditions, the immediate product of the reaction, the monodehydroascorbate radical, is reduced back to ascorbate by a monodehydroascorbate reductase (monodehydroascorbate reductase (NADH)) enzyme. APX is an integral component of the glutathione-ascorbate cycle.

Source: Professor Koichi Koshiba, Tokyo Metropolitan University Graduate School of Science and Technology Department of Life Science

References:
Koshiba, T. (1993) Cytosolic ascorbate peroxidase in seeds and leaves of maize (Zea mays). Plant Cell Physiol. 34: 713-721.