5xd9
Crystal structure analysis of 3,6-anhydro-L-galactonate cycloisomerase
Structural highlights
FunctionACI_VIBSJ Involved in the degradation of 3,6-anhydro-L-galactose, which is the major monomeric sugar of red macroalgae. Catalyzes the isomerization of 3,6-anhydrogalactonate (AHGA) to 2-keto-3-deoxy-galactonate (KDGal).[1] Publication Abstract from PubMed3,6-Anydro-l-galatonate cycloisomerase (ACI) catalyzes the cycloisomerization of a 3,6-anhydro-l-galactonic acid known as a novel metabolite in agarolytic bacteria. Here, we present 3-D structures of ACI from Vibrio sp. strain EJY3 (VejACI) in native and mutant forms at 2.2 A and 2.6 A resolutions, respectively. The enzyme belongs to the mandelate racemase subgroup of the enolase superfamily catalyzing common beta-elimination reactions by alpha-carbon deprotonation of substrates. The structure of VejACI revealed a notable 20s loop region in the capping domain, which can be a highly conserved structural motif in ACI homologs of agar metabolism. By comparing mutant (mVejAC/H300 N) and native VejACI structures, we identified a conformational change of Ile142 in VejACI that causes spatial expansion in the binding pocket. These observations imply that Ile142 and the 20s loop play important roles in enzymatic reactivity and substrate specificity. The structural phylogenetic analysis of the enolase superfamily including ACIs revealed sequential, structural, and functional relationships related to the emergence of novel substrate specificity. Crystal structure analysis of 3,6-anhydro-l-galactonate cycloisomerase suggests emergence of novel substrate specificity in the enolase superfamily.,Lee S, Kim KH, Kim HY, Choi IG Biochem Biophys Res Commun. 2017 Sep 9;491(1):217-222. doi:, 10.1016/j.bbrc.2017.07.080. Epub 2017 Jul 14. PMID:28716734[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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