DOI: 10.5176/2251-2489_BioTech13.33
Authors: Nidhee Chaudhary, Subhash Chand, Nameet Kaur
Abstract:
Free radicals have been implicated in the etiology of several human diseases as well as ageing. Oxidative stress, induced by oxygen free radicals (Reactive oxygen species: ROS), is believed to be a primary factor in various degenerative diseases, such as cancer, atherosclerosis, gastric ulcer and other conditions. It is suggested that free radical damage to cells leads to the pathological changes associated with aging and may also be a contributory factor in a progressive decline in the function of the immune system. Co-operative defense systems that protect the body from free radical damage include the anti-oxidant nutrients and enzymes. The anti-oxidant enzymes include superoxide dismutase (SOD), catalase, glutathione peroxidase (GSH-px) and indirectly glutathione reductase. Identification of anti-oxidants remains a highly active research area due to their potential to reduce the risk of various chronic diseases caused by free radicals. Many antioxidant compounds, naturally occurring from plant sources, have been identified as a free radical or active oxygen scavengers. Recently, interest has increased considerably in finding naturally occurring antioxidants for use in foods or medicinal materials to replace synthetic antioxidants, which are being restricted due to their side effects such as carcinogenicity. In addition, natural antioxidants have the capacity to improve food quality and stability and can also act as nutraceuticals to terminate free radical chain reactions in biological systems, and thus may provide additional health benefits to consumers. Antioxidant based drugs/formulations for prevention and treatment of complex diseases like atherosclerosis, stroke, diabetes, Alzheimer’s disease (AD), Parkinson’s disease, cancer, etc. appeared over the past three decades. Dietary antioxidants may have promising therapeutic potential in delaying the onset as well as in preventing ageing population with its related complications. Superoxide free radical (O2-.) (ROS) is a strong oxidant and damage other molecules and the cell structures of which they are a part. Superoxide Dismutase (SOD: 1.15.1.1) is an ubiquitous, antioxidant enzyme (oxidoreductase) that protect other chemicals of the body from damage due to oxidation reactions. It catalyzes the dismutation of the super oxide radical into hydrogen peroxide and molecular oxygen and plays a central role in protecting against oxidative stress. It is an endogenously produced intracellular enzyme present in essentially every cell in the body and has great role in the cell’s defense against ROS. This defense system becomes increasingly important as more pathological and disease states are examined and it is discovered that oxidative damage is a cause, if not a critical player. Reducing the threat is possible by strengthening and reinforcing the body's natural levels of SOD through nutritional supplements and a diet rich in antioxidants.
Treatments currently being developed, to target the SOD role in scavenging ROS, and thus, attenuate the damage resulting from oxidative stress, may take one of several approaches: 1. Enhancement of the cell’s SOD abilities, often using natural extracts. 2. Use of SOD mimetics, and 3. Supplementary enzyme therapy. SOD acts as both an antioxidant and anti-inflammatory in the body, neutralizing the free radicals that can lead to wrinkles and precancerous cell changes. The potential of superoxide dismutase as an anti-aging treatment is being explored, since it is now known that SOD levels drop while free radical levels increase with aging. Superoxide Dismutase has also been used to treat arthritis, prostate problems, corneal ulcers, burn injuries, inflammatory diseases, inflammatory bowel disease, and long-term damage from exposure to smoke and radiation, and to prevent side effects of cancer drugs. In its topical form, it may help to reduce facial wrinkles, scar tissue, heal wounds and burns, lighten dark or hyper pigmentation, and protect against harmful UV rays. Due to its wide applications, SOD has great prospects in the industries like; pharmaceuticals, cosmetics, food and/or biotechnology. An important requirement for enzymes intended for industrial applications is their thermo-stability, as thermal denaturation is a common cause of their inactivation. In the present study, thermostable SOD has been isolated and characterized from Ribes nigrum; a dry fruit. The SOD enzyme obtained has been partially purified into two fractions based on 0-40{6e6090cdd558c53a8bc18225ef4499fead9160abd3419ad4f137e902b483c465} and 40-80{6e6090cdd558c53a8bc18225ef4499fead9160abd3419ad4f137e902b483c465} saturation level of ammonium sulphate; 0-40{6e6090cdd558c53a8bc18225ef4499fead9160abd3419ad4f137e902b483c465} fraction (66.5 Units/mg) having higher specific activity. The temperature optima of the partially purified SOD lied between 350C to 400C with thermostability up to 70°C whereas the optimum value for pH being 6.0 with stability range of 5.0-7.0. Amongst the tested detergents; the enzyme inhibition was found in the descending order as Sodium Lauryl Sulphate (SLS), Tween-20 and Tween-80. Cween-20 did not affect the activity of enzyme. Various univalent and bivalent ions in the form of their respective salts were used to perform inhibition studies. They were found to inhibit SOD activity in the given order: Na+ >Ba2+ >Ca2+ >K+. Barium and Sodium ions showed about 50{6e6090cdd558c53a8bc18225ef4499fead9160abd3419ad4f137e902b483c465} reduction in enzyme activity with inhibition constants (Ki) values being 2.4 mM and 1.6 mM, respectively. The results obtained herein indicate that R. nigrum being an excellent source of natural dietery antioxidant enzyme, has great potential as functional food. It can be inferred from the present study that R. nigrum, a dry fruit rich in sugars and other nutrients, is also a promising source of SOD, which in turn has application in oxidative stress-related diseases. The thermo-stability of the enzyme further enhances its importance making it industry friendly with high economical feasibility. Further studies are needed to explore the potential of such therapeutically important products, along with their use as supplement in various medicinal formulations.
Keywords: Superoxide dismutase; Ribes nigrum; Thermostable.
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