1.1.1.361: glucose-6-phosphate 3-dehydrogenase

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Bacillus subtilis 168

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D-glucose 6-phosphate + NAD+

3-dehydro-D-glucose 6-phosphate + NADH + H+

Bacillus subtilis

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725212

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the enzyme catalyzes the first step in kanosamine biosynthesis

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the alpha-anomer form is the substrate for the enzyme. Kinetics of NtdC by itself and with the next enzyme in the pathway, NtdA, which converts 3-oxo-D-glucose 6-phosphate to kanosamine 6-phosphate through a glutamate-coupled PLP-dependent transamination, have shown that the equilibrium of both the NtdC reaction and the NtdC-NtdA-coupled reaction lies heavily toward D-glucose 6-phosphate

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the enzyme obeys a random sequential mechanism, with nearly equal Km values for NAD+ and D-glucose 6-phosphate

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Bacillus subtilis 168

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the alpha-anomer form is the substrate for the enzyme. Kinetics of NtdC by itself and with the next enzyme in the pathway, NtdA, which converts 3-oxo-D-glucose 6-phosphate to kanosamine 6-phosphate through a glutamate-coupled PLP-dependent transamination, have shown that the equilibrium of both the NtdC reaction and the NtdC-NtdA-coupled reaction lies heavily toward D-glucose 6-phosphate

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additional information

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Bacillus subtilis

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no substrate: UDP-glucose

725212

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the NtdC-catalyzed reaction is unusual because 3-oxo-D-glucose 6-phosphate undergoes rapid ring opening, resulting in a 1,3-dicarbonyl compound that is inherently unstable due to enolate formation. Synthesis of carbocyclic G6P analogues by two routes, one based upon the Ferrier II rearrangement to generate the carbocycle and one based upon a Claisen rearrangement. Both pseudo-anomers of carbaglucose 6-phosphate (C6P) are synthesized using the Ferrier approach, and activity assays reveal that the pseudo-alpha-anomer is a good substrate for NtdC, while the pseudo-beta-anomer and the open-chain analogue, sorbitol 6-phosphate (S6P), are not substrates. A more efficient synthesis of alpha-C6P is achieved using the Claisen rearrangement approach, which allows for a thorough evaluation of the NtdC-catalyzed oxidation of alpah-C6P

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under alkaline conditions, the product is not stable because of ring opening followed by deprotonation of the 1,3-dicarbonyl compound. Hydride transfer from carbon 3 is partially rate-limiting in the enzymatic reaction, and deuterium substitution on carbon 2 has no significant effect on the enzymatic reaction but lowers the rate of deprotonation of 3-dehydro-D-glucose 6-phosphate 4fold. Kinetics of the NtdC catalyzed reaction in the presence of the next enzyme in the pathway, NtdA. As the amount of NtdA is increased, the rate of the NtdC reaction also increases up to a maximum when NtdA exceeds a 20:1 molar ratio relative to NtdC. No change in the pH-rate profile for the coupled reaction is observed compared to that of the uncoupled assay

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under alkaline conditions, the product is not stable because of ring opening followed by deprotonation of the 1,3-dicarbonyl compound. Hydride transfer from carbon 3 is partially rate-limiting in the enzymatic reaction, and deuterium substitution on carbon 2 has no significant effect on the enzymatic reaction but lowers the rate of deprotonation of 3-dehydro-D-glucose 6-phosphate 4fold. Kinetics of the NtdC catalyzed reaction in the presence of the next enzyme in the pathway, NtdA. As the amount of NtdA is increased, the rate of the NtdC reaction also increases up to a maximum when NtdA exceeds a 20:1 molar ratio relative to NtdC. No change in the pH-rate profile for the coupled reaction is observed compared to that of the uncoupled assay

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Bacillus subtilis 168

the NtdC-catalyzed reaction is unusual because 3-oxo-D-glucose 6-phosphate undergoes rapid ring opening, resulting in a 1,3-dicarbonyl compound that is inherently unstable due to enolate formation. Synthesis of carbocyclic G6P analogues by two routes, one based upon the Ferrier II rearrangement to generate the carbocycle and one based upon a Claisen rearrangement. Both pseudo-anomers of carbaglucose 6-phosphate (C6P) are synthesized using the Ferrier approach, and activity assays reveal that the pseudo-alpha-anomer is a good substrate for NtdC, while the pseudo-beta-anomer and the open-chain analogue, sorbitol 6-phosphate (S6P), are not substrates. A more efficient synthesis of alpha-C6P is achieved using the Claisen rearrangement approach, which allows for a thorough evaluation of the NtdC-catalyzed oxidation of alpah-C6P

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under alkaline conditions, the product is not stable because of ring opening followed by deprotonation of the 1,3-dicarbonyl compound. Hydride transfer from carbon 3 is partially rate-limiting in the enzymatic reaction, and deuterium substitution on carbon 2 has no significant effect on the enzymatic reaction but lowers the rate of deprotonation of 3-dehydro-D-glucose 6-phosphate 4fold. Kinetics of the NtdC catalyzed reaction in the presence of the next enzyme in the pathway, NtdA. As the amount of NtdA is increased, the rate of the NtdC reaction also increases up to a maximum when NtdA exceeds a 20:1 molar ratio relative to NtdC. No change in the pH-rate profile for the coupled reaction is observed compared to that of the uncoupled assay