Lee Jun Hyuck, Bae Jungdon, Kim Dooil, Choi Yongseok, Im Young Jun, Koh Sukhoon, Kim Joong Su, Kim Mun-Kyoung, Kang Gil Bu, Hong Suk-In, Lee Dae-Sil, Eom Soo Hyun
Department of Life Science, Gwangju Institute of Science and Technology, Republic of Korea.
Biochem Biophys Res Commun. 2006 Sep 1;347(3):616-25. doi: 10.1016/j.bbrc.2006.06.139. Epub 2006 Jul 5.
It was recently established that fructose-1,6-bisphosphate (FBP) aldolase (FBA) and tagatose-1,6-bisphosphate (TBP) aldolase (TBA), two class II aldolases, are highly specific for the diastereoselective synthesis of FBP and TBP from glyceraldehyde-3-phosphate (G3P) and dihydroxyacetone phosphate (DHAP), respectively. In this paper, we report on a FBA from the thermophile Thermus caldophilus GK24 (Tca) that produces both FBP and TBP from C(3) substrates. Moreover, the FBP:TBP ratio could be adjusted by manipulating the concentrations of G3P and DHAP. This is the first native FBA known to show dual diastereoselectivity among the FBAs and TBAs characterized thus far. To explain the behavior of this enzyme, the X-ray crystal structure of the Tca FBA in complex with DHAP was determined at 2.2A resolution. It appears that as a result of alteration of five G3P binding residues, the substrate binding cavity of Tca FBA has a greater volume than those in the Escherichia coli FBA-phosphoglycolohydroxamate (PGH) and TBA-PGH complexes. We suggest that this steric difference underlies the difference in the diastereoselectivities of these class II aldolases.
最近确定,果糖-1,6-二磷酸(FBP)醛缩酶(FBA)和塔格糖-1,6-二磷酸(TBP)醛缩酶(TBA)这两种II类醛缩酶,分别对从3-磷酸甘油醛(G3P)和磷酸二羟丙酮(DHAP)非对映选择性合成FBP和TBP具有高度特异性。在本文中,我们报道了一种来自嗜热栖热菌GK24(Tca)的FBA,它能从C(3)底物生成FBP和TBP。此外,通过控制G3P和DHAP的浓度可以调节FBP与TBP的比例。这是已知的第一种在迄今所表征的FBA和TBA中显示出双重非对映选择性的天然FBA。为了解释这种酶的行为,以2.2埃分辨率测定了与DHAP复合的Tca FBA的X射线晶体结构。似乎由于五个G3P结合残基的改变,Tca FBA的底物结合腔比大肠杆菌FBA-磷酸甘油羟肟酸(PGH)和TBA-PGH复合物中的底物结合腔体积更大。我们认为这种空间差异是这些II类醛缩酶非对映选择性差异的基础。