Nucleotide sugar dehydratases: Structure, mechanism, substrate specificity, and application potential

Reaction Mechanism and Three-Dimensional Structure of GDP-d-glycero-α-d-manno-heptose 4,6-Dehydratase from Campylobacter jejuni

“…The proposed reaction mechanism for the conversion of GDP- d -glycero-α- d -manno-heptose ( 3 ) to GDP-6-deoxy-4-keto-α- d -lyxo-heptose ( 4 ) is presented in Scheme . ,− In the first step, the tightly bound NAD + is used to oxidize C4 of the substrate to generate GDP- d -glycero-4-keto-α- d -lyxo-heptose ( 7 ) and NADH. In the second step, water is eliminated from C5/C6 due to the increased acidity of the hydrogen at C5 to form intermediate 8 .…”

“…jejuni NCTC 11168, the final heptose moiety is d -glycero- l -gluco-heptose, whereas in C. jejuni 81-176, it can either be 6-deoxy-α- d - altro -heptose (as shown in Figure ) or d -glycero-α- d - altro -heptose. , In the biosynthesis of the modified 6-deoxy-heptose sugars, GDP- d -glycero-α- d -manno-heptose ( 3 ) is first dehydrated to GDP-6-deoxy-4-keto-α- d -lyxo-heptose ( 4 ). , The oxidation of C4 renders the adjacent stereocenters at C3 and C5 susceptible to isomerization by an epimerase. − In the final step, a C4 reductase establishes the ultimate stereochemistry at C4. This combination of enzymes can thus generate up to eight different compounds that are stereochemically different at C3, C4, or C5.…”

“…Efforts have been made previously to understand the heptose modification pathways more completely in the CPS of C. jejuni by isolating and characterizing the enzymes that are responsible for the conversion of GDP- d -glycero-α- d -manno-heptose ( 3 ) to various modified heptoses. − The Creuzenet laboratory cloned, purified, and biochemically characterized two key enzymes within the 6-deoxy- d - altro -heptose biosynthesis pathway in C. jejuni 81-176, namely DdahA and DdahB. ,, DdahA (also known as WcbK) was shown to be a GDP- d -glycero-α- d -manno-heptose 4,6-dehydratase that catalyzes the committed step in the formation of 6-deoxy-heptoses in C.…”

“…On the basis of this structure, seven site-directed variants were constructed to test their role in the catalytic reaction mechanism of this 4,6-dehydratase. The reaction is proposed to proceed through the oxidation of C4 by the tightly bound NAD + , followed by the loss of water from C5/C6 to form the unsaturated ketone intermediate . The ultimate product is made via the reduction of the C5/C6 double bond by the tightly bound NADH produced during the oxidation of C4.…”

Metatranscriptome sequencing identifies Escherichia are major contributors to pathogenic functions and biofilm formation in diabetes related foot osteomyelitis

“…K01710 (dTDP-glucose 4,6-dehydratase rfbB, rmlB, rffG ) was abundant across all but four bone specimens. dTDP-D-glucose 4,6-dehydratase is an enzyme which catalyzes the dehydration of the nucleotide sugar dTDP- D-glucose (Vogel et al, 2022 ). L-rhamnose is found in the cell walls and envelopes of many pathogenic Gram-negative and some Gram-positive bacteria (Mäki and Renkonen, 2004 ), and the enzyme is an important constituent of the L-rhamnose biosynthetic pathway which is involved in a variety of biological functions including bacterial fitness (Solheim et al, 2014 ; Koller and Lassak, 2021 ) growth (van der Beek et al, 2019 ), virulence (Allard et al, 2002 ; Zulianello et al, 2006 ), extracellular polysaccharide (EPS) (Whitfield and Paiment, 2003 ; Mistou et al, 2016 ), and lipopolysaccharide (LPS) production (King et al, 2009 ; Franzosa et al, 2018 ).…”