Zatón A M, Ochoa de Aspuru E
Departamento de Bioquímica y Biología Molecular, Universidad del País Vasco, Facultad de Farmacia, Vitoria-Gasteiz, España.
FEBS Lett. 1995 Oct 30;374(2):192-4. doi: 10.1016/0014-5793(95)01088-v.
In this paper, the activity of horseradish peroxidase was further determined in the presence of several uracil derivatives. The rate of guaiacol peroxidation decreases in presence of 2-thiouracil and of 6-n-propyl-2-thiouracil, but is not changed by 6-n-propyluracil nor uracil. Thus, thiouracils inhibit horseradish peroxidase in a noncompetitive form. The binding of 6-n-propyl-2-thiouracil, 2-thiouracil, 6-n-propyluracil and uracil with horseradish peroxidase shows difference spectra due to changes in the environment of heme group in peroxidase. Then, the binding sites for these uracil derivatives are in an hydrophobic pocket at the heme periphery of peroxidase. The lesser binding rates were for uracil and propyluracil, which did not inhibit the peroxidase activity. These results point to the thiol group in uracils as responsible for the inhibition of peroxidase activity through interaction with an allosteric binding site, in peroxidase heme environment.
在本文中，在几种尿嘧啶衍生物存在的情况下进一步测定了辣根过氧化物酶的活性。在2-硫尿嘧啶和6-正丙基-2-硫尿嘧啶存在时，愈创木酚过氧化速率降低，但6-正丙基尿嘧啶和尿嘧啶对其无影响。因此，硫尿嘧啶以非竞争性形式抑制辣根过氧化物酶。6-正丙基-2-硫尿嘧啶、2-硫尿嘧啶、6-正丙基尿嘧啶和尿嘧啶与辣根过氧化物酶的结合由于过氧化物酶中血红素基团环境的变化而呈现差异光谱。那么，这些尿嘧啶衍生物的结合位点位于过氧化物酶血红素外周的疏水口袋中。尿嘧啶和丙基尿嘧啶的结合率较低，它们不抑制过氧化物酶活性。这些结果表明，尿嘧啶中的巯基通过与过氧化物酶血红素环境中的变构结合位点相互作用，从而抑制过氧化物酶活性。
