Mark W. Ruszczycky

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UDP-galactopyranose mutase (UGM) requires reduced FAD (FAD(red)) to catalyze the reversible interconversion of UDP-galactopyranose (UDP-Galp) and UDP-galactofuranose (UDP-Galf). Recent structural and mechanistic studies of UGM have provided evidence for the existence of an FAD-Galf/p adduct as an intermediate in the catalytic cycle. These findings are(More)
The Diels-Alder reaction is a [4+2] cycloaddition reaction in which a cyclohexene ring is formed between a 1,3-diene and an electron-deficient alkene via a single pericyclic transition state. This reaction has been proposed as a key transformation in the biosynthesis of many cyclohexene-containing secondary metabolites. However, only four purified enzymes(More)
Only a very few examples of enzymes known to catalyze pericyclic reactions have been reported, and presently no enzyme has been demonstrated unequivocally to catalyze a Diels-Alder reaction. Nevertheless, research into secondary metabolism has led to the discovery of numerous natural products exhibiting the structural hallmarks of [4+2] cycloadditions,(More)
D-desosamine (1) is a 3-(N,N-dimethylamino)-3,4,6-trideoxyhexose found in a number of macrolide antibiotics including methymycin (2), neomethymycin (3), pikromycin (4), and narbomycin (5) produced by Streptomyces venezuelae . It plays an essential role in conferring biological activities to its parent aglycones. Previous genetic and biochemical studies of(More)
DesII from Streptomyces venezuelae is a radical SAM (S-adenosyl-l-methionine) enzyme that catalyzes the deamination of TDP-4-amino-4,6-dideoxy-d-glucose to form TDP-3-keto-4,6-dideoxy-d-glucose in the biosynthesis of TDP-d-desosamine. DesII also catalyzes the dehydrogenation of the nonphysiological substrate TDP-D-quinovose to TDP-3-keto-6-deoxy-d-glucose.(More)
Among the TEM-type extended-spectrum beta-lactamases (ESBLs), an amino acid change at Ambler position 104 (Glu to Lys) results in increased resistance to ceftazidime and cefotaxime when found with other substitutions (e.g., Gly238Ser and Arg164Ser). To examine the role of Asp104 in SHV beta-lactamases, site saturation mutagenesis was performed. Our goal was(More)
Tartrate dehydrogenase catalyzes the reductive decarboxylation of meso-tartrate to glycerate. Concomitant with the ketonization of the intermediate enolate the C3 hydroxymethylene of glycerate necessarily acquires a proton from solvent. In D2O, the proton is shown to be added stereospecifically to form (2R,3R)-[3-2H]glycerate. The 1H-NMR assignments of the(More)
DesII, a radical S-adenosyl-l-methionine (SAM) enzyme from Streptomyces venezuelae, catalyzes the deamination of TDP-4-amino-4,6-dideoxy-D-glucose to TDP-3-keto-4,6-dideoxy-D-glucose in the desosamine biosynthetic pathway. DesII can also catalyze the dehydrogenation of TDP-D-quinovose to the corresponding 3-keto sugar. Similar to other radical SAM enzymes,(More)
The radical S-adenosyl-L-methionine enzyme DesII from Streptomyces venezuelae is able to oxidize the C3 hydroxyl group of TDP-D-quinovose to the corresponding ketone via an α-hydroxyalkyl radical intermediate. It is unknown whether electron transfer from the radical intermediate precedes or follows its deprotonation, and answering this question would offer(More)
Carbohydrates play a key role in the biological activity of numerous natural products. In many instances their biosynthesis requires radical mediated rearrangements, some of which are catalyzed by radical SAM enzymes. BtrN is one such enzyme responsible for the dehydrogenation of a secondary alcohol in the biosynthesis of 2-deoxystreptamine. DesII is(More)