McEldoon J P, Dordick J S
Department of Chemical and Biochemical Engineering, University of Iowa, Iowa City 52242.
J Biol Chem. 1991 Aug 5;266(22):14288-93.
Horseradish peroxidase has been shown to catalyze the oxidation of veratryl alcohol (3,4-dimethoxybenzyl alcohol) and benzyl alcohol to the respective aldehydes in the presence of reduced glutathione, MnCl2, and an organic acid metal chelator such as lactate. The oxidation is most likely the result of hydrogen abstraction from the benzylic carbon of the substrate alcohol leading to eventual disproportionation to the aldehyde product. An aromatic cation radical intermediate, as would be formed during the oxidation of veratryl alcohol in the lignin peroxidase-H2O2 system, is not formed during the horseradish peroxidase-catalyzed reaction. In addition to glutathione, dithiothreitol, L-cysteine, and beta-mercaptoethanol are capable of promoting veratryl alcohol oxidation. Non-thiol reductants, such as ascorbate or dihydroxyfumarate (known substrates of horseradish peroxidase), do not support oxidation of veratryl alcohol. Spectral evidence indicates that horseradish peroxidase compound II is formed during the oxidation reaction. Furthermore, electron spin resonance studies indicate that glutathione is oxidized to the thiyl radical. However, in the absence of Mn2+, the thiyl radical is unable to promote the oxidation of veratryl alcohol. In addition, Mn3+ is unable to promote the oxidation of veratryl alcohol in the absence of glutathione. These results suggest that the ultimate oxidant of veratryl alcohol is a Mn(3+)-GSH or Mn(2+)-GS. complex (where GS. is the glutathiyl radical).
已表明辣根过氧化物酶在还原型谷胱甘肽、MnCl₂和诸如乳酸盐的有机酸金属螯合剂存在的情况下，能催化藜芦醇（3,4 - 二甲氧基苄醇）和苄醇氧化成各自的醛。这种氧化很可能是底物醇的苄基碳上的氢被夺取，最终歧化成醛产物的结果。在木质素过氧化物酶 - H₂O₂体系中藜芦醇氧化过程中会形成的芳香阳离子自由基中间体，在辣根过氧化物酶催化的反应中不会形成。除了谷胱甘肽外，二硫苏糖醇、L - 半胱氨酸和β - 巯基乙醇也能够促进藜芦醇氧化。非硫醇还原剂，如抗坏血酸盐或二羟基富马酸盐（辣根过氧化物酶的已知底物），不支持藜芦醇氧化。光谱证据表明在氧化反应过程中形成了辣根过氧化物酶化合物II。此外，电子自旋共振研究表明谷胱甘肽被氧化成硫自由基。然而，在没有Mn²⁺的情况下，硫自由基无法促进藜芦醇氧化。另外，在没有谷胱甘肽的情况下，Mn³⁺也无法促进藜芦醇氧化。这些结果表明藜芦醇的最终氧化剂是Mn(3 +)-GSH或Mn(2 +)-GS复合物（其中GS.是谷胱甘肽硫自由基）。
