title: A retro-evolution study of CDP-6-deoxy-D-glycero-L-threo-4-hexulose-3-dehydrase (E1) from Yersinia pseudotuberculosis: implications for C-3 deoxygenation in the biosynthesis of 3,6-dideoxyhexoses.
abstract: CDP-6-deoxy-l-threo-d-glycero-4-hexulose-3-dehydrase (E1), which catalyzes C-3 deoxygenation of CDP-4-keto-6-deoxyglucose in the biosynthesis of 3,6-dideoxyhexoses, shares a modest sequence identity with other B6-dependent enzymes, albeit with two important distinctions. It is a rare example of a B6-dependent enzyme that harbors a [2Fe-2S] cluster, and a highly conserved lysine that serves as an anchor for PLP in most B6-dependent enzymes is replaced by histidine at position 220 in E1. Since alteration of His220 to a lysine residue may produce a putative progenitor of E1, the H220K mutant was constructed and tested for the ability to process the predicted substrate, CDP-4-amino-4,6-dideoxyglucose, using PLP as the coenzyme. Our data showed that H220K-E1 has no dehydrase activity, but can act as a PLP-dependent transaminase. However, the reaction is not catalytic since PLP cannot be regenerated during turnover. Reported herein are the results of this investigation and the implications for the role of His220 in the catalytic mechanism of E1.
authors.affiliation: Division of Medicinal Chemistry, College of Pharmacy, and Department of Chemistry and Biochemistry, University of Texas, Austin, Texas 78712, USA.
authors.forename: Qingquan
authors.initials: Q
authors.lastname: Wu
authors.forename: Yung-Nan
authors.initials: YN
authors.lastname: Liu
authors.forename: Huawei
authors.initials: H
authors.lastname: Chen
authors.forename: Erich J
authors.initials: EJ
authors.lastname: Molitor
authors.forename: Hung-wen
authors.initials: HW
authors.lastname: Liu
mesh_terms: D019943:Amino Acid Substitution; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002384:Catalysis; D006601:Hexoses / Q000096:biosynthesis* / Q000737:chemistry; D006836:Hydro-Lyases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020125:Mutation, Missense; D025101:Vitamin B 6 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D015011:Yersinia pseudotuberculosis / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D006601:Hexoses; C009616:tyvelose; D025101:Vitamin B 6; C073141:CDP-4-keto-6-deoxy-D-glucose-3-dehydrase; D006836:Hydro-Lyases