title: Oxidative stress response of Inonotus obliquus induced by hydrogen peroxide.
abstract: While the medicinal fungus Inonotus obliquus produces polyphenols as one of its main metabolites in natural habitats, it accumulates less polyphenols under laboratory conditions. In this study we found that the continuous addition of 1 mM H(2)O(2) at a rate of 1.6 ml/h into a submerged culture of the fungus enhanced its production of mycelia, melanins, flavonoids and hispidin analogs (HA). Simultaneous exposure of the fungus to both H(2)O(2) and arbutin resulted in reduced production of mycelia, glycosylated flavonoids (GF) and HA, and inhibition of melanogenesis. However, superoxide dismutases (SOD) and catalase (CAT) activity were enhanced following the addition of H(2)O(2) or H(2)O(2) plus arbutin. The maximum levels of SOD and CAT activities reached 355.2 U/mg protein and 39.8 U/mg protein respectively in H(2)O(2)-added medium, and 264 U/mg protein and 35.9 U/mg protein respectively in H(2)O(2) plus arbutin medium. Thus, detoxification of H(2)O(2) is conducted mainly by polyphenols under normal physiological conditions, and by both polyphenols and antioxidant enzymes under oxidative stress when melanogenesis is inhibited. Although enhanced HA production occurred after melanogenesis inactivation, total extracellular polyphenol levels were reduced. These findings suggest that enzymatic activities convert superoxide to H(2)O(2), and non-enzymatic mechanisms are largely responsible for detoxifying H(2)O(2). Enhanced production of melanins is the most important non-enzymatic response of this fungus against oxidative stress.
authors.affiliation: Key Laboratory for Biotechnology on Medicinal Plants of Jiangsu Province, Xuzhou Normal University, Xuzhou, China. zheng.weifa@gmail.com
authors.forename: Weifa
authors.initials: W
authors.lastname: Zheng
authors.forename: Yanxia
authors.initials: Y
authors.lastname: Zhao
authors.forename: Meimei
authors.initials: M
authors.lastname: Zhang
authors.forename: Zhiwen
authors.initials: Z
authors.lastname: Wei
authors.forename: Kangjie
authors.initials: K
authors.lastname: Miao
authors.forename: Weiguo
authors.initials: W
authors.lastname: Sun
mesh_terms: D000704:Analysis of Variance; D001487:Basidiomycota / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism*; D018533:Biomass; D002374:Catalase / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D005419:Flavonoids / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D008543:Melanins / Q000378:metabolism; D025282:Mycelium / Q000254:growth & development / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects*; D011753:Pyrones / Q000378:metabolism; D013482:Superoxide Dismutase / Q000378:metabolism
chemical_list: D005419:Flavonoids; D008543:Melanins; D011753:Pyrones; D006861:Hydrogen Peroxide; D002374:Catalase; D013482:Superoxide Dismutase; C007946:hispidin