同源(β/α)8-barrel无关的酶催化反应:orotidine 5 '一磷酸脱羧酶和3-keto-L-gulonate 6-phosphate脱羧酶。
文章的细节
-
引用
复制到剪贴板 -
明智的E,紫杉WS,巴比特PC, Gerlt是的,Rayment我
同源(β/α)8-barrel无关的酶催化反应:orotidine 5 '一磷酸脱羧酶和3-keto-L-gulonate 6-phosphate脱羧酶。
生物化学。2002年3月26日,41 (12):3861 - 9。
- PubMed ID
-
11900527 (在PubMed]
- 文摘
-
的3-keto-L-gulonate 6-phosphate脱羧酶(KGPDC)由ulaD基因在大肠杆菌基因组中编码(紫杉,w·S。Gerlt, j·a·j . Bacteriol(2002)。184年,302 - 306]和orotidine 5 '一磷酸脱羧酶(OMPDC)同源(源自共同的祖先),但不同催化反应。metal-independent的脱羧反应催化乙烯阴离子的OMPDC避免形成中间;Mg2 +端依赖所催化的脱羧反应KGPDC涉及enediolate阴离子形成的中间。OMPDC的基于可用的结构序列比对可以预测(1)KGPDC的二聚体(β/α)8-barrels,活跃的站点位于二聚体界面;(2)KGPDC最后OMPDC共享一个天冬氨酸残基的第一个beta-strand和Asp-x-Lys-x-x-Asp主题的第三beta-strand OMPDC;但(3)KGPDC Glu而不是第二beta-strand年底赖氨酸。KGPDC的结构已经确定在Mg2 +和底物类似物L-gulonate 6-phosphate和证实这些预测。的羧酸盐官能团的第一,第二,第三在KGPDC beta-strands Mg2 +配体;在OMPDC,这些残留的同系物参与氢键网络,促进了脱羧反应。 The 3-OH group of the substrate analogue is coordinated to the Mg2+, supporting the hypothesis that the mechanism of the decarboxylation catalyzed by KGPDC involves stabilization of an enediolate anion intermediate. These structural studies establish the existence of the OMPDC "suprafamily," in which members catalyze reactions that occur in different metabolic pathways and share no mechanistic relationship. The existence of this suprafamily demonstrates that divergent evolution can be opportunistic, conscripting active site features of a progenitor to catalyze unrelated functions. Accordingly, sequence or structure homology alone cannot be used to infer the functions of new proteins discovered in genome projects.