The deoxy sugars which have been found ubiquitously in plants, fungi and bacteria, are an important class of carbohydrate. The widespread occurrence of deoxy sugars in different organisms suggest diverse biological functions. Numerous reports have shown that they indeed exhibit various vital and potent biological activities. Interest in the chemistry and biochemistry of deoxy sugars has expanded considerably due to the studies of bacterial surface glycans in which a number of dideoxy hexoses have been identified as important antigenic determinants in bacteria. Although the importance of this type of sugar in affecting the immune response is well recognized, little is known about their biosynthetic formation. Furthermore, in the studies of 3,6-dideoxyhexose, many unique features of the enzymes involved in this biological transformation have been found. These unusual properties are not readily explicable, and thus offer a challenge to our understanding of fundamental enzymatic mechanisms. Inspired by the intriguing biological activities of this type sugar and the unique catalytic properties of the enzymes involved in its biosynthesis, we will examine this biosynthetic process at the molecular level. Initial efforts will be directed to the biosynthesis of 3,6-dideoxyhexose, and emphasis will be placed on the mechanistic and stereochemical aspects. Specifically, we will (1) purify the enzymes involved in the biosynthetic formation of ascarylose (3,6-dideoxy-L-arabino-hexose); (2) synthesize isotopically labeled substrates and cofactors, and potential alternate substrates containing mechanistically informative reactive functionality at key sites of the molecules; (3) incubate these compounds with the enzymes, determine their competence as substrates and/or inhibitors, and determine the structures of the incubation products in order to address the following mechanistic and stereochemical points of general importance to the understanding of all deoxy sugar biosynthesis: (a) the overall stereochemical outcome of this dehydration-reduction process; (b) mechanism of sugar reduction; and (c) mechanism of NAD(P)H oxidation. The possible presence and role of metal ion in this catalysis will be carefully examined. With everything well under way, we will proceed with the study of other deoxy sugar biosynthesis, such as the formation of 2,6-dideoxyhexoses. Evaluation of the results from these experiments will aid in forming a conclusion about the nature and sequence of events at the active-site of these important enzymes during these biosynthetic transformations.

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University of Minnesota Twin Cities
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Ko, Yeonjin; Lin, Geng-Min; Ruszczycky, Mark W et al. (2018) Mechanistic Implications of the Deamination of TDP-4-amino-4-deoxy-d-fucose Catalyzed by the Radical SAM Enzyme DesII. Biochemistry 57:3130-3133
Besandre, Ronald; Liu, Hung-Wen (2018) Biochemical Basis of Vosevi, a New Treatment for Hepatitis CPublished as part of the Biochemistry series ""Biochemistry to Bedside"". Biochemistry 57:479-480
Ruszczycky, Mark W; Zhong, Aoshu; Liu, Hung-Wen (2018) Following the electrons: peculiarities in the catalytic cycles of radical SAM enzymes. Nat Prod Rep 35:615-621
Ko, Yeonjin; Wang, Shao-An; Ogasawara, Yasushi et al. (2017) Identification and Characterization of Enzymes Catalyzing Pyrazolopyrimidine Formation in the Biosynthesis of Formycin A. Org Lett 19:1426-1429
Bridwell-Rabb, Jennifer; Zhong, Aoshu; Sun, He G et al. (2017) A B12-dependent radical SAM enzyme involved in oxetanocin A biosynthesis. Nature 544:322-326
Lin, Chia-I; McCarty, Reid M; Liu, Hung-Wen (2017) The Enzymology of Organic Transformations: A Survey of Name Reactions in Biological Systems. Angew Chem Int Ed Engl 56:3446-3489
Ruszczycky, Mark W; Liu, Hung-Wen (2017) Theory and Application of the Relationship Between Steady-State Isotope Effects on Enzyme Intermediate Concentrations and Net Rate Constants. Methods Enzymol 596:459-499
Lin, Geng-Min; Romo, Anthony J; Liem, Priscilla H et al. (2017) Identification and Interrogation of the Herbicidin Biosynthetic Gene Cluster: First Insight into the Biosynthesis of a Rare Undecose Nucleoside Antibiotic. J Am Chem Soc 139:16450-16453
Kim, Hak Joong; Liu, Yung-Nan; McCarty, Reid M et al. (2017) Reaction Catalyzed by GenK, a Cobalamin-Dependent Radical S-Adenosyl-l-methionine Methyltransferase in the Biosynthetic Pathway of Gentamicin, Proceeds with Retention of Configuration. J Am Chem Soc 139:16084-16087
Ruszczycky, Mark W; Liu, Hung-Wen (2017) Biochemistry: The surprising history of an antioxidant. Nature 551:37-38

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