A multiple role for the coenzyme in the mechanism of action of 6-phosphogluconate dehydrogenase. The oxidative decarbosylation of 2-deoxy-6-phosphogluconate.

Abstract 6-Phosphogluconate dehydrogenase from Candida utilis catalyzes the oxidative decarboxylation of 2-deoxy-6-phosphogluconate. The 3-keto-2-deoxy-6-phosphogluconate, an intermediate of the reaction, is reduced to 2-deoxy-6-phosphogluconate and decarboxylated to 1-deoxyribulose 5-phosphate when incubated with the enzyme and TPNH. The decarboxylation process does not occur in the absence of the reduced coenzyme, which does not have, in this step, an oxidation-reduction role. Since TPNH also has a non-redox role in a tritium exchange reaction catalyzed by the enzyme, it appears that the coenzyme has a multiple role in the mechanism of action of 6-phosphogluconate dehydrogenase: a redox role in the dehydrogenation and another (or others) role(s) in the decarboxylation and tritium exchange reactions. The hydroxyl group present at carbon 2 of 6-phosphogluconate seems to have a dual role in the mechanism of action of the enzyme: one in the binding of the substrate to the enzyme, another in enhancing the decarboxylation of the dehydrogenation product. These findings are discussed with relations to the mechanism of action of isocitrate dehydrogenase and of the malic enzyme. The enzymatic oxidative decarboxylation of 2-deoxy-6-phosphogluconate is a new step for the metabolism of the metabolic inhibitor 2-deoxyglucose

Thermodynamic characterization of substrate and inhibitor binding to Trypanosoma brucei 6-phosphogluconate dehydrogenase

6-Phosphogluconate dehydrogenase is a potential target for new drugs against African trypanosomiasis. Phosphorylated aldonic acids are strong inhibitors of 6-phosphogluconate dehydrogenase, and 4-phospho-d-erythronate (4PE) and 4-phospho-d-erythronohydroxamate are two of the strongest inhibitors of the Trypanosoma brucei enzyme. Binding of the substrate 6-phospho-d-gluconate (6PG), the inhibitors 5-phospho-d-ribonate (5PR) and 4PE, and the coenzymes NADP, NADPH and NADP analogue 3-amino-pyridine adenine dinucleotide phosphate to 6-phospho-d-gluconate dehydrogenase from T. brucei was studied using isothermal titration calorimetry. Binding of the substrate (K(d) = 5 microm) and its analogues (K(d) =1.3 microm and K(d) = 2.8 microm for 5PR and 4PE, respectively) is entropy driven, whereas binding of the coenzymes is enthalpy driven. Oxidized coenzyme and its analogue, but not reduced coenzyme, display a half-site reactivity in the ternary complex with the substrate or inhibitors. Binding of 6PG and 5PR poorly affects the dissociation constant of the coenzymes, whereas binding of 4PE decreases the dissociation constant of the coenzymes by two orders of magnitude. In a similar manner, the K(d) value of 4PE decreases by two orders of magnitude in the presence of the coenzymes. The results suggest that 5PR acts as a substrate analogue, whereas 4PE mimics the transition state of dehydrogenation. The stronger affinity of 4PE is interpreted on the basis of the mechanism of the enzyme, suggesting that the inhibitor forces the catalytic lysine 185 into the protonated state

Vaginal Lactoferrin Modulates PGE 2

Inflammation plays an important role in pregnancy, and cytokine and matrix metalloproteases (MMPs) imbalance has been associated with premature rupture of membranes and increased risk of preterm delivery. Previous studies have demonstrated that lactoferrin (LF), an iron-binding protein with anti-inflammatory properties, is able to decrease amniotic fluid (AF) levels of IL-6. Therefore, we aimed to evaluate the effect of vaginal LF administration on amniotic fluid PGE2 level and MMP-TIMP system in women undergoing genetic amniocentesis. One hundred and eleven women were randomly divided into controls (n = 57) or treated with LF 4 hours before amniocentesis (n = 54). Amniotic fluid PGE2, active MMP-9 and MMP-2, and TIMP-1 and TIMP-2 concentrations were determined by commercially available assays and the values were normalized by AF creatinine concentration. PGE2, active MMP-9, and its inhibitor TIMP-1 were lower in LF-treated group than in controls (p < 0.01, p < 0.005, and p < 0.001, resp.). Conversely, active MMP-2 (p < 0.0001) and MMP-2/TIMP-2 molar ratio (p < 0.001) were increased, whilst TIMP-2 was unchanged. Our data suggest that LF administration is able to modulate the inflammatory response following amniocentesis, which may counteract cytokine and prostanoid imbalance that leads to abortion. This trial is registered with Clinical Trial number NCT02695563

Clinical correlates of “pure” essential tremor: the TITAN study

BackgroundTo date, there are no large studies delineating the clinical correlates of “pure” essential tremor (ET) according to its new definition.MethodsFrom the ITAlian tremor Network (TITAN) database, we extracted data from patients with a diagnosis of “pure” ET and excluded those with other tremor classifications, including ET-plus, focal, and task-specific tremor, which were formerly considered parts of the ET spectrum.ResultsOut of 653 subjects recruited in the TITAN study by January 2022, the data of 208 (31.8%) “pure” ET patients (86M/122F) were analyzed. The distribution of age at onset was found to be bimodal. The proportion of familial cases by the age-at-onset class of 20 years showed significant differences, with sporadic cases representing the large majority of the class with an age at onset above 60 years. Patients with a positive family history of tremor had a younger onset and were more likely to have leg involvement than sporadic patients despite a similar disease duration. Early-onset and late-onset cases were different in terms of tremor distribution at onset and tremor severity, likely as a function of longer disease duration, yet without differences in terms of quality of life, which suggests a relatively benign progression. Treatment patterns and outcomes revealed that up to 40% of the sample was unsatisfied with the current pharmacological options.DiscussionThe findings reported in the study provide new insights, especially with regard to a possible inversed sex distribution, and to the genetic backgrounds of “pure” ET, given that familial cases were evenly distributed across age-at-onset classes of 20 years. Deep clinical profiling of “pure” ET, for instance, according to age at onset, might increase the clinical value of this syndrome in identifying pathogenetic hypotheses and therapeutic strategies

The allosteric site of sendai virus hemagglutinin neuraminidase

none3noneBellini T.; Tomasi M.; Dallocchio F.Bellini, Tiziana; Tomasi, M.; Dallocchio, Franco Pasquale Filipp

Subunits asymmetry in the ternary complex of lamb liver 6-phophogluconate dehydrogenase detected by a NADP analogue

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