天冬氨酸氨基转移酶与红汞的相互作用。酶的一个暴露巯基与活性中心的关系。
Interaction of aspartate aminotransferase with mercurochrome. Relationship of an exposed thiol group of the enzyme to the active centre.
作者信息
Kalogerakos T G, Oikonomakos N G, Dimitropoulos C G, Karni-katsadima I A, Evangelopoulos A E
出版信息
Biochem J. 1977 Oct 1;167(1):53-63. doi: 10.1042/bj1670053.
Mercurochrome strongly inhibits aspartate transaminase and 2,3-dicarboxyethylated aspartate transaminase. The native enzyme exhibits a biphasic time-course of inactivation by mercurochrome with second-order rate constants 1.62 x 10(4) M-1 - min-1 and 2.15 x 10(3) M-1 - min-1, whereas the modified enzyme is inactivated more slowly (second-order rate constant 6.1 x 10(2) M-1 - min-1) under the same conditions. The inhibitor inactivates native and modified enzyme in the absence as well as in the presence of substrates. Mercurochrome-transaminase interaction is accompanied by a red shift in the absorption maximum of the fluorochrome of about 10 nm. Difference spectra of the mercurochrome-enzyme system versus mercurochrome, compared with analogous spectra of mercurochrome-ethanol, revealed that the spectral shifts recorded during mercurochrome-transaminase interaction are similar to those that occur when mercurochrome is dissolved in non-polar solvents. Studies of mercurochrome complexes with native or modified transaminase, isolated by chromatography on Sephadex G-25, revealed that native transaminase is able to conjugate with four mercurochrome molecules per molecule, but the modified enzyme is able to conjugate with only two mercurochrome molecules per molecule.
红汞强烈抑制天冬氨酸转氨酶和2,3 - 二羧乙基化天冬氨酸转氨酶。天然酶被红汞灭活呈现双相时间进程，二级速率常数分别为1.62×10⁴ M⁻¹·min⁻¹和2.15×10³ M⁻¹·min⁻¹，而在相同条件下，修饰后的酶灭活更慢（二级速率常数6.1×10² M⁻¹·min⁻¹）。该抑制剂在有无底物存在的情况下均可使天然酶和修饰酶失活。红汞与转氨酶相互作用时，荧光染料的最大吸收波长会发生约10 nm的红移。与红汞 - 乙醇的类似光谱相比，红汞 - 酶体系相对于红汞的差示光谱表明，红汞与转氨酶相互作用过程中记录到的光谱变化类似于红汞溶解于非极性溶剂时发生的变化。对通过Sephadex G - 25柱层析分离得到的红汞与天然或修饰转氨酶的复合物的研究表明，天然转氨酶每个分子能够与四个红汞分子结合，但修饰后的酶每个分子仅能与两个红汞分子结合。
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