Conroy J M, Salter R D
Mol Immunol. 1982 May;19(5):659-63. doi: 10.1016/0161-5890(82)90366-2.
Rabbit antisera specific for horseradish peroxidase inhibit the catalytic activity of the enzyme. All antibodies prepared against the holoenzyme react with the peroxidase apoenzyme. However, only a minority (30-45%) of the total antiperoxidase pool cross react with reduced and alkylated apoenzymes. The antibodies inhibiting peroxidase activity do not bind to S-carboxymethyl of S-carboxamidomethylated apoenzyme derivatives as measured by absorption and competition of inhibition experiments. Glycopeptides derived from horseradish peroxidase also failed to bind anticatalytic antibodies. Antibodies that inhibit enzyme activity have specificity for noncarbohydrate conformation dependent antigenic determinants of horseradish peroxidase. Additional experiments probed the mechanism by which inhibitory antibody decreases the catalytic activity of horseradish peroxidase. Absorption spectra of horseradish peroxidase that has bound Fab fragments sufficient to cause 90% inhibition of the enzyme activity determined that the enzyme retained the ability to bind hydrogen peroxide. Thus, anticatalytic antibodies do not prevent the formation of the first enzyme-substrate intermediate but mediate their inhibitory effects by disrupting a later step in the reaction mechanism.
辣根过氧化物酶特异性兔抗血清可抑制该酶的催化活性。所有针对全酶制备的抗体均与过氧化物酶脱辅基酶蛋白发生反应。然而，在总的抗过氧化物酶库中，只有少数（30 - 45%）与还原型和烷基化脱辅基酶蛋白发生交叉反应。通过吸收和抑制竞争实验测定，抑制过氧化物酶活性的抗体不与S - 羧甲基化或S - 羧酰胺甲基化脱辅基酶衍生物的S - 羧甲基结合。来源于辣根过氧化物酶的糖肽也不能结合抗催化抗体。抑制酶活性的抗体对辣根过氧化物酶的非碳水化合物构象依赖性抗原决定簇具有特异性。额外的实验探究了抑制性抗体降低辣根过氧化物酶催化活性的机制。结合足以导致该酶活性90%抑制的Fab片段的辣根过氧化物酶的吸收光谱表明，该酶保留了结合过氧化氢的能力。因此，抗催化抗体并不阻止第一种酶 - 底物中间体的形成，而是通过破坏反应机制中的后续步骤来介导其抑制作用。
