Ullman E F, Yoshida R A, Blakemore J I, Maggio E, Leute R
Biochim Biophys Acta. 1979 Mar 16;567(1):66-74. doi: 10.1016/0005-2744(79)90173-6.
Pig heart mitochondrial malate dehydrogenase (L-malate:NAD+ oxidoreductase, EC 1.1.1.37) is about 90% inhibited upon labelling an average of two amino groups per subunit with an active ester of thyroxine. Inhibition is probably associated primarily with thyroxine binding to one specific group which is normally unreactive but becomes activated upon noncovalent binding of thyroxine derivatives to the enzyme. Enzyme inhibition is due to a decrease in the rate of association of NAD. Antibodies to thyroxine induce a slow conformational change with partial reversal of inhibition of more heavily labelled conjugates. The antibody-induced activation is not cooperative and does not require bivalent association of the antibody. Activation can be blocked by the presence of free thyroxine and is the basis for a clinically useful assay for serum thyroxine.
猪心脏线粒体苹果酸脱氢酶（L-苹果酸：NAD⁺氧化还原酶，EC 1.1.1.37）在用甲状腺素活性酯对每个亚基平均标记两个氨基后，约90%受到抑制。抑制作用可能主要与甲状腺素结合到一个特定基团有关，该基团通常无反应性，但在甲状腺素衍生物与酶非共价结合后被激活。酶的抑制是由于NAD结合速率降低所致。甲状腺素抗体诱导缓慢的构象变化，使标记程度更高的缀合物的抑制作用部分逆转。抗体诱导的激活不具有协同性，也不需要抗体的二价结合。游离甲状腺素的存在可阻断激活，这是血清甲状腺素临床有用检测方法的基础。
