L-苏氨酸醛缩酶在大鼠肝脏中并非一种真正的酶。
L-threonine aldolase is not a genuine enzyme in rat liver.
作者信息
Yeung Y G
出版信息
Biochem J. 1986 Jul 1;237(1):187-90. doi: 10.1042/bj2370187.
Activity of L-threonine aldolase in rat liver cytosolic extract was not affected by the omission of alcohol dehydrogenase in a previously established NADPH-linked alcohol dehydrogenase-coupled assay. The liver extract was able to catalyse the dehydrogenation of NADPH with either acetaldehyde (a product of L-threonine aldolase action) or 2-oxobutyrate (a product of L-threonine dehydratase action). When the liver extract was chromatographed on a Sephacryl S-200 column, no threonine aldolase activity was detected in the eluate. However, activity of threonine aldolase re-appeared when the fractions with highest activity of lactate dehydrogenase and threonine dehydratase were mixed. Activity of threonine aldolase could also be abolished by removing threonine dehydratase from the liver extract with a specific antibody. Hence L-threonine aldolase should not be a genuine enzyme in the rat liver, and the apparent enzyme activity may result from a combined effect of threonine dehydratase and lactate dehydrogenase (or an oxo acid-linked NADPH dehydrogenase) in the liver cytosolic extract.
在先前建立的与NADPH偶联的乙醇脱氢酶偶联测定中，大鼠肝脏胞质提取物中L-苏氨酸醛缩酶的活性不受乙醇脱氢酶缺失的影响。肝脏提取物能够利用乙醛（L-苏氨酸醛缩酶作用的产物）或2-氧代丁酸（L-苏氨酸脱水酶作用的产物）催化NADPH的脱氢反应。当肝脏提取物在Sephacryl S-200柱上进行层析时，洗脱液中未检测到苏氨酸醛缩酶活性。然而，当将乳酸脱氢酶和苏氨酸脱水酶活性最高的组分混合时，苏氨酸醛缩酶活性重新出现。用特异性抗体从肝脏提取物中去除苏氨酸脱水酶也可消除苏氨酸醛缩酶的活性。因此，L-苏氨酸醛缩酶不应是大鼠肝脏中的一种真正的酶，其表观酶活性可能是肝脏胞质提取物中苏氨酸脱水酶和乳酸脱氢酶（或一种氧代酸偶联的NADPH脱氢酶）共同作用的结果。
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