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天冬氨酸转氨甲酰酶

天冬氨酸转氨甲酰酶
识别
符号 CAD
Entrez 790
HUGO 1424
OMIM 114010
RefSeq NM_004341
UniProt P27708
其他数据
EC编号 2.1.3.2
基因座 2 p22-p21

天冬氨酸转氨甲酰酶(英语:Aspartate carbamoyltransferaseEC 2.1.3.2,简称为ATCase)是嘧啶核苷酸从头合成中很重要的一个,它催化的是天冬氨酸与氨甲酰磷酸生成氨甲酰天冬氨酸磷酸的反应。

动力学

作为别构酶的典型例子。v-[S]图为S型,而不是一般米-门二氏酶的双曲线形,希尔系数>1。这表明,ATC酶的活性随底物浓度增加而增加,具有正协同性。

ATC酶的活性受嘧啶合成终产物CTP的反馈抑制,这主要发生在反应的最初阶段。同时也受到ATP的激活,以调和嘌呤/嘧啶核苷酸的合成。

结构与别构效应

据William Lipscomb的X线分析结果,大肠杆菌的ATC酶结构为C6R6,共由12个亚基组成。其中催化亚基由两个三量体C3,调节亚基由三个二量体R2组成。两个催化三量体构成该酶的两个主要面,调节二聚体构成酶的几个角,呈三角形。[1]

经过分离的C3同样具有活性,且Vmax大于原ATC酶,并显示出无协同性的饱和曲线。也不受ATP/CTP影响。而分离的R2可与别构调节子结合,但不具有催化作用。这证明了原ATC酶中催化亚基与调节亚基相互作用并控制反应活性。[1]

据别构调节假说,激活剂ATP优先与ATC酶的活性型(R),抑制剂CTP则优先与其非活性型(T)结合。


该酶的竞争性抑制剂为N-膦乙酰基-L-天冬氨酸(PALA)。他不具有反应性,但只与活性型结合。

外部链接

参考文献

  1. ^ 1.0 1.1 Voet, Donald; Voet, Judith G.; Pratt, Charlotte W.; Tamiya, nobuo; Yagi, tatsuhiko; Endo, toshiya; Yoshihisa, toru; 田宫, 信雄(1922-2011); 八木, 达彦(1933- ). Voto kiso seikagaku.. 基礎生化学第5版. 东京化学同人. 2017: 254–256. ISBN 978-4-8079-0925-4. OCLC 1022202113. 
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天冬氨酸转氨甲酰酶
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