Dataset Information

UDP-glucose Dehydrogenase: The First-step Oxidation Is an NAD⁺-dependent Bimolecular Nucleophilic Substitution Reaction (S_N2).

ABSTRACT: UDP-glucose dehydrogenase (UGDH) catalyzes the conversion of UDP-glucose to UDP-glucuronic acid by NAD⁺-dependent two-fold oxidation. Despite extensive investigation into the catalytic mechanism of UGDH, the previously proposed mechanisms regarding the first-step oxidation are somewhat controversial and inconsistent with some biochemical evidence, which instead supports a mechanism involving an NAD⁺-dependent bimolecular nucleophilic substitution (S_N2) reaction. To verify this speculation, the essential Cys residue of Streptococcus zooepidemicus UGDH (SzUGDH) was changed to an Ala residue, and the resulting Cys260Ala mutant and SzUGDH were then co-expressed in vivo via a single-crossover homologous recombination method. Contrary to the previously proposed mechanisms, which predict the formation of the capsular polysaccharide hyaluronan, the resulting strain instead produced an amide derivative of hyaluronan, as validated via proteinase K digestion, ninhydrin reaction, FT-IR and NMR. This result is compatible with the NAD⁺-dependent S_N2 mechanism.

SUBMITTER: Chen J

PROVIDER: S-EPMC6367545 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature

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Publications

UDP-glucose Dehydrogenase: The First-step Oxidation Is an NAD+-dependent Bimolecular Nucleophilic Substitution Reaction (SN2).

Chen Jun J Yu Yang Y Gao Jiaojiao J Yang Shulin S

International journal of biological sciences 20190101 2

UDP-glucose dehydrogenase (UGDH) catalyzes the conversion of UDP-glucose to UDP-glucuronic acid by NAD+-dependent two-fold oxidation. Despite extensive investigation into the catalytic mechanism of UGDH, the previously proposed mechanisms regarding the first-step oxidation are somewhat controversial and inconsistent with some biochemical evidence, which instead supports a mechanism involving an NAD+-dependent bimolecular nucleophilic substitution (SN2) reaction. ...[more]

PMID: 30745825

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Project description:Organoboranes are among the most versatile and widely used reagents in synthetic chemistry. A significant further expansion of their application spectrum would be achievable if boron-containing reactive intermediates capable of inserting into C-H bonds or performing nucleophilic substitution reactions were readily available. However, current progress in the field is still hampered by a lack of universal design concepts and mechanistic understanding. Herein we report that the doubly arylene-bridged diborane(6) 1H2 and its B 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 B-bonded formal deprotonation product Li2[1] can activate the particularly inert C(sp3)-H bonds of added H3CLi and H3CCl, respectively. The first case involves the attack of [H3C]- on a Lewis-acidic boron center, whereas the second case follows a polarity-inverted pathway with nucleophilic attack of the B 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 B double bond on H3CCl. Mechanistic details were elucidated by means of deuterium-labeled reagents, a radical clock, ?,?-dihaloalkane substrates, the experimental identification of key intermediates, and quantum-chemical calculations. It turned out that both systems, H3CLi/1H2 and H3CCl/Li2[1], ultimately funnel into the same reaction pathway, which likely proceeds past a borylene-type intermediate and requires the cooperative interaction of both boron atoms.

Dataset Information

UDP-glucose Dehydrogenase: The First-step Oxidation Is an NAD⁺-dependent Bimolecular Nucleophilic Substitution Reaction (S_N2).

Publications

UDP-glucose Dehydrogenase: The First-step Oxidation Is an NAD<sup>+</sup>-dependent Bimolecular Nucleophilic Substitution Reaction (S<sub>N</sub>2).

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