4-Uloses as Intermediates in Enzyme-Nicotinamide Adenine Dinucleotide-mediated Oxidoreductase Mechanisms
| Autor: | Adair Wl, Othmar Gabriel, Stathakos D, Herman M. Kalckar |
|---|---|
| Rok vydání: | 1973 |
| Předmět: |
Adenosine monophosphate
chemistry.chemical_classification biology Chemistry Stereochemistry nutritional and metabolic diseases Active site Substrate (chemistry) Cell Biology Nicotinamide adenine dinucleotide Biochemistry nervous system diseases Adenosine diphosphate chemistry.chemical_compound Enzyme Oxidoreductase mental disorders biology.protein NAD+ kinase Molecular Biology |
| Zdroj: | Journal of Biological Chemistry. 248:4640-4648 |
| ISSN: | 0021-9258 |
| DOI: | 10.1016/s0021-9258(19)43711-3 |
| Popis: | A decrease in enzymatic activity during the standard assay procedure for UDP-galactose-4-epimerase (EC 5.1.3.2) led to the observation that ADP-ribose-(5) (5-(adenosine-5'-pyrophosphoryl)d-ribose), a degradation product of NAD+, is a strong inhibitor for the enzyme. This inhibition was completely reversed by the addition of TDP-4-keto-6-deoxyglucose. Synthetic analogues of ADP-ribose-(5), such as TDP-ribose-(5) and TDP-glucose-(6) were found to be even better inhibitors than ADP-ribose-(5). Incubation of UDP-galactose-4-epimerase with TDP-[1-3H]glucose-(6) established the reaction mechanism of the inhibition as follows: TDP-[1-3H]glucose-(6) + enzyme·NAD+ → (TDP-gluconic acid-(6)·enzyme-[3H1]NADH). We call this process "reductive inhibition." One criterion used to recognize reductive inhibition is the reversal of this process by the addition of TDP-4-keto-6-deoxyglucose: (TDP-gluconic acid-(6)·enzyme·[3H1]NADH) + TDP-4-keto-6-deoxyglucose → enzyme·NAD+ + TDP-gluconic acid-(6) + TDP-6-deoxy-[4-3H]glucose + TDP-6-deoxy-[4-3H]galactose. These results, in combination with a stereochemical examination of the hydrogen mediation of the substrate as well as of the reductive inhibitor, led us to conclude that the same active site on the enzyme is involved in both processes. The concept of reductive inhibition is illustrated and applied to other groups of compounds as well as to other enzymes. In all cases discussed, reductive inhibition occurs according to the following scheme: 3H-inhibitor + enzyme·NAD+ → ((Inhibitor)oxidized ·enzyme-[3H1]NADH) |
| Databáze: | OpenAIRE |
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