再请教一个问题， 转氨酶在体内是如何降解的？

baobao7676

肝细胞凋亡后释放转氨酶到血清中和淋巴液，但[size=20.7999992370605px]转氨酶作为大分子， 是如何在体内降解的呢？一般教科书提到ALT的半衰期47小时， 但未提及具体机制， 希望有高手释疑。

bigben446

被肝组织里面的肝窦内皮细胞吸收并降解
1985年hepatology的一篇文章专门回答你的问题

Hepatology. 1985 May-Jun;5(3):367-75.
Plasma clearance of intravenously injected aspartate aminotransferase isozymes: evidence for preferential uptake by sinusoidal liver cells.
Kamimoto Y, Horiuchi S, Tanase S, Morino Y.
Abstract
Both cytosolic (c-AAT) and mitochondrial (m-AAT) isozymes of aspartate aminotransferase (EC 2.6.1.1) appear in serum in some diseases including hepatobiliary dysfunction. The present study aimed at elucidation of the mechanism by which AAT isozymes are cleared from blood. Intravenous injection into rats of m-AAT and c-AAT purified from rat liver exhibited a biphasic clearance curve with an overall half-life of 42 min and 4.7 hr, respectively. The tissue distribution of the radioactivity following intravenous administration of 125I-labeled isozymes revealed that the liver is a major organ involved in plasma clearance of these isozymes. This conclusion was also supported by the significant retardation in plasma clearance of m-AAT in hepatectomized as well as CCl4-intoxicated rats. Furthermore, clearance rate of each AAT isozyme in an isolated perfused liver exhibited a single exponential process with the uptake rate for m-AAT being much faster than that for c-AAT. Separation of hepatocytes and sinusoidal liver cells from the rat intravenously injected with 125I-labeled AAT isozymes revealed that sinusoidal cells were responsible for the plasma clearances. In vitro uptake study showed that both isozymes were exclusively taken up by sinusoidal liver cells. The uptake rate for m-AAT was considerably greater than that for c-AAT. Endocytotic index for uptake by sinusoidal cells was 16 times with c-AAT and 34 times with m-AAT as compared with that for inulin or dextran which are taken up by fluid-phase endocytosis, suggesting involvement of adsorptive endocytosis in the uptake of the isozymes.
PMID: 3997068 [PubMed - indexed for MEDLINE]

http://onlinelibrary.wiley.com/d ... 1840050305/abstract

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谢谢版主大人！