Saurabh Pandey, Yogesh Kuma
The existence of isoform diversity among antioxidant enzymes contributes to the spatial and temporal fine tuning of cellular responses. In plants heme binding ascorbate peroxidase (APX) (EC, 220.127.116.11) presents a crucial line of defense against reactive oxygen species. The present study aims to provide a comparative view of the functional attributes of major isoforms of APX in plants species. A total of 64 protein sequences of APX were subjected to homology search, multiple sequence alignment, phylogenetic tree construction, and motif analysis. The phylogenetic tree constructed revealed different clusters based on heme binding APX in respect of dicot and monocot plants such as different source of plant species represented by Oryza sativa, Arabidopsis thaliana, Sorghum bicolor, Zea mays, Ricinus communis, Populus trichocarpa, Vitis vinifera, and Selaginella moellendorffii. The multiple sequence alignment of these APX protein sequences from different plants showed conserved regions at different stretches with maximum homology in amino acid residues. The motif analysis revealed a conserved peroxidase domain uniformly observed in all APX irrespective of variable plant species suggesting its possible role in structural and enzymatic functions. The signature amino acids sequence of VFYQMGLSDKDIVALSGGHTLGRCH, NNGLHIAIRLCQPIKEQFPIITYADFYQLAGVVAVEVTGGPTIPMHPGRV and LFEDPSFRPYVEKYAKDQDAFFKDYAEAHMKLSELGF, related with the plant heme binding peroxidase as well as chloroplastic and cytosolic peroxidase signature was frequently observed and seemed to be related with the structure and enzymatic function in all APX protein sequences. The findings of the present study may be useful for designing degenerate primers or probes specific for APX and possibly presents the first line of defense amongst all the APX isoforms involved in the cellular antioxidant defense pathway, during exposure to abiotic stresses.