Activation of Dioxygen in an Aqueous System of [(FeTMPyP)-T-III]-MBTH-O-2 to Form Peroxide and Azine from MBTH: Reactivity of Superoxohemin ([(FeTMPyP)-T-III-OO](center dot)) and Peroxohemin ([(FeTMPyP)-T-III-OO](-))

作者：Nakano Taku^*; Kakuda Hiroko; Shinoda Hiroyuki; Moriyama Hiroshi

来源：Bulletin of the Chemical Society of Japan, 2013, 86(5): 620-627.

DOI：10.1246/bcsj.20120328

Activation of dioxygen in the heme system is observed in an artificial aqueous model system. It has been demonstrated that in the system of a water-soluble hemin, tetrakis(N-methylpyridyl)porphinatoiron(III) pentachloride ([(FeTMPyP)-T-III]Cl-5), and a mild reducing reagent, 3-methyl-2-benzothiazolinonehydrazone (MBTH), a superoxide anion radical and hydrogen peroxide have been produced in air at pH 7.0 that degrades hemin. In this complex system with a reductant and an oxidant, we have found the reaction products derived from MBTH: a bridging peroxide, 2,2%26apos;-peroxybis(3-methyl-2,3-dihydrobenzothiazole) (MBTPO), adding to a previously observed azine, 1,2-bis(3-methyl-2,3-dihydrobenzothiazole-2-ylidene)hydrazine (MBTA), and also a small amount of ketone, 3-methyl-2(3H)-benzothiazolone (MBTZ). We suggest that dioxygen is activated to the intermediates, superoxohemin ([Fe-III-OO](center dot)) and peroxohemin ([Fe-III-OO](-)). Because the addition of reactive oxygen species quenchers such as superoxide dismutase (SOD) and catalase allows reaction that prevents the degradation of heme, the roles of liberated superoxide or hydrogen peroxide are excluded from the mechanism. On the other hand, another possible intermediate, a high-valent oxoiron species ([Fe+=O]), is suggested to form the ketone, MBTZ, while under anaerobic conditions organic hydropercodde (t-BuOOH) instead of O-2 solely reacts to form the ketone. The system is discussed in relation to NADPH oxidase, cytochrome P450, NO synthase (NOS), and heme oxidase (HO).

• 出版日期2013-5-15