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>Lipoxygenase from potato tubers. Partial purification and properties of an enzyme that specifically oxygenates the 9-position of linoleic acid
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Lipoxygenase from potato tubers. Partial purification and properties of an enzyme that specifically oxygenates the 9-position of linoleic acid
pA lipoxygenase (EC 1.13.1.13) was partially purified from potato tubers and was shown to differ from previously characterized soya-bean lipoxygenases in the positional specificity and pH characteristics of the oxygenation reaction. The potato enzyme converted linoleic acid almost exclusively (95%) into 9-d-hydroperoxyoctadeca-itrans/i-10,icis/i-12-dienoic acid. The 13-hydroperoxy isomer was only a minor product (5%). Linolenic acid was an equally effective substrate, which was also oxygenated specifically at the 9-position. The enzyme had a pH optimum at 5.5–6.0 and was inactive at pH9.0. A half-maximal velocity was obtained at a linoleic acid concentration of 0.1mm. No inhibition was observed with EDTA (1mm) and cyanide (1mm) or with ip/i-chloromercuribenzoate (0.2mm). Haemoproteins were not involved in the lipoxygenase activity. The molecular weight of the enzyme was estimated from gel filtration to be approx. 10sup5/sup. Preliminary evidence suggested that the enzyme oxygenated the in/i–10 position of fatty acids containing a penta(in/i–3, in/i–6)diene structure./p
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机译:p脂氧合酶(EC 1.13.1.13)从马铃薯块茎中部分纯化,并显示出与先前表征的大豆脂氧合酶在氧合反应的位置特异性和pH特性方面不同。马铃薯酶几乎完全(95%)将亚油酸转化为9-d-氢过氧十八烷基-反式-10,顺式-12-二烯酸。 13-氢过氧异构体仅是次要产物(5%)。亚麻酸是同样有效的底物,它也专门在9位被氧化。该酶的最佳pH值在5.5-6.0,在pH9.0时无活性。在0.1mm的亚油酸浓度下获得半最大速度。用EDTA(1mm)和氰化物(1mm)或对-氯汞苯甲酸酯(0.2mm)未观察到抑制作用。血红素蛋白不参与脂氧合酶活性。通过凝胶过滤估计该酶的分子量约为1。 10 5 sup>。初步证据表明,该酶氧化了含有五( n i> -3, n i> -6)二烯结构的脂肪酸的 n i> -10位置 p>
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