A Defense Associated Peroxidase from Lemon Having Dye Decolorizing Ability and Offering Resistance to Heat, Heavy Metals and Organic Solvents

Abstract

Peroxidases have ability to catalyze redox reaction of a wide range of phenolic as well as non-phenolic compounds and exhibited various physiological roles in plant life cycle. From the point of view of industrial applications of peroxidases, the isolation and characterization of peroxidases offering resistance to higher pH and temperature, salts, organic solvents is highly desirable. In this direction, a partial cDNA clone of peroxidase from lemon was isolated and characterized. The peroxidase was found to be defense associated as evident by the higher expression in diseased condition than that of healthy one at both the transcript and enzymatic activity levels. This defense related peroxidase from lemon leaves was purified to homogeneity using quick two step processes of heat treatment and affinity chromatography. The native peroxidase was found to be a heterotrimer of 200 kDa, consisting of two subunits each of 66 kDa while, one subunit of 70 kDa. The purified peroxidase was found to be stable towards heat (retained 92% activity at 80°C for 1 h) and organic solvents, namely ethanol, methanol and isopropanol (retained 30-50% activity in the presence of 50% (v/v) of these solvents for 1 h). Purified peroxidase also exhibited tolerance to heavy metal ions such as Cd 2+ , Ni 2+ and Cs 2+ . The purified lemon peroxidase was found to efficiently oxidize the industrial dyes in the order of aniline blue>methyl orange> indigo carmine >trypan blue > crystal violet, such that 40-54% dye decolorization was observed within 4 h. Thus, the properties exhibited by purified lemon peroxidase make it a promising candidate enzyme for industrial exploitation.

Breakthroughs in the discovery and use of different peroxidase isoforms of microbial origin

“…Plant peroxidases are used in a variety of biotechnological applications [8] , [11] . Even though, their exploitation is often hampered by their notoriously difficult heterologous expression and limited stability, plant peroxidases are rendered as attractive biocatalysts due to their neutral optimum pH, their wide substrate specificity which enables them to use various synthetic chromophores as electron donors [40] .…”

“…Animal peroxidases belong to the PCOXS superfamily and they are responsible for biological processes such as innate immunity, defense responses, immune system or hormone regulation [1] , [11] , [21] . Enzymes such as myeloperoxidase (MPO), lactoperoxidase (LPO) and thyroid peroxidase (TPO) belong to this group of peroxidases.…”

“…In the past decade, various peroxidases capable of effectively degrading dyes have been identified from other sources such as white turnip, bitter ground, and horseradish. Accordingly, the newly identified peroxidase isoforms of MxG could be added to the list of effective dye degrading peroxidase sources [11] , [34] , [54] .…”

“…The discovery of organic solvent resistant peroxidase is of great importance. The lemon enzyme discovered from C. limon was found to exhibit maximum tolerance towards methanol solvent followed by ethanol and isopropanol [11] . With regards to its dye decolorization abilities, the obtained lemon peroxidase was able to effectively decolorize five out of the seven dyes tested.…”

“…The reduction of peroxides at the expense of electron donating substrates is what makes peroxidase enzymes useful in several biotechnological applications. Many peroxidase enzymes of particular interest are already being used as organic catalysts in numerous processes in various industries ( Table 1 ) [8] , [11] , [19] , [20] .…”