SOLUBLE AND MEMBRANE-BOUND PIG LIVER MITOCHONDRIAL MONOAMINE-OXIDASE - THERMOSTABILITY, TRYPTIC DIGESTABILITY AND KINETIC PROPERTIES
SOLUBLE AND MEMBRANE-BOUND PIG LIVER MITOCHONDRIAL MONOAMINE-OXIDASE - THERMOSTABILITY, TRYPTIC DIGESTABILITY AND KINETIC PROPERTIES
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DOI：
10.1016/0006-2952(72)90419-4
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发表时间：
1972-01-01
影响因子：
5.8
通讯作者：
EKSTEDT, B
中科院分区：
文献类型：
--
作者：
ORELAND, L;EKSTEDT, B
此前已有研究表明，猪肝单胺氧化酶(单胺：O2氧化还原酶，EC 1.4.3.4)可通过甲乙酮萃取而溶解于缓冲液中。在强酸性磷脂存在下，可溶性酶能反弹到脱脂的膜上，与线粒体结合的酶和可溶性酶的热稳定性比较表明，可溶性酶比结合酶更不稳定。可溶性酶重新结合到修复的膜上，部分恢复了热稳定性。可溶性酶比结合在线粒体上的酶对胰酶更敏感。可溶酶与复制膜的重新结合不会降低其对胰酶的敏感性。讨论了膜组分在稳定酶分子中的作用。两种酶的酪胺氧化速率随温度的变化是相同的。骆驼蓬碱对结合酶和可溶性酶的可逆抑制程度相同。在酪胺和5-羟色胺为底物的情况下也是如此。然而，任何一种形式的酶对5-羟色胺的氧化都比酪胺的氧化受到更大的抑制。Pargyline不可逆地抑制酪胺和5-羟色胺的氧化，对结合酶和可溶性酶都是如此。酶从膜上解离后，其分子活性没有发生变化。根据这些发现，讨论了猪肝脏中存在多种形式的单胺氧化酶的可能性。
It has previously been shown that pig liver monoamine oxidase (monoamine: O2oxidoreductase, EC 1.4.3.4) can be rendered soluble in buffer by extraction with methylethyl ketone. The soluble enzyme can be rebound to delipidated membranes in the presence of highly acidic phospholipids.A comparison of the thermostabilities of the enzyme bound to the mitochondria and the soluble form showed that the soluble enzyme was much more labile than the bound enzyme. Rebinding of the soluble enzyme to relipidated membranes partially restored the thermostability. The soluble enzyme was more sensitive to tryptic digestion than the enzyme bound to mitochondria. Rebinding of the soluble enzyme to replipidated membranes did not decrease its sensitivity to trypsin. The role of membrane components in stabilizing the enzyme molecule is discussed.The change in the rate of tyramine oxidation with temperature was the same for both forms of the enzyme.Harmaline was found to reversibly inhibit both bound and soluble enzyme to the same degree. This was true both with tyramine and serotonin as substrate. However, serotonin oxidation by either form of the enzyme was inhibited more than tyramine oxidation. Pargyline irreversibly inhibited tyramine and serotonin oxidation to the same degree, both with the bound and the soluble enzyme. The molecular activity of the enzyme did not change after liberation from the membrane. The possibility that there are multiple forms of monoamine oxidase in the pig liver is discussed in the light of these findings.