Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.5.1.1 (asparaginase)
 2,695 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The structures of Erwinia chrysanthemi L-asparaginase (ErA) complexed with the L- and D-stereoisomers of the suicide inhibitor, 6-diazo-5-oxy-norleucine, have been solved using X-ray crystallography and refined with data extending to 1.7 A. The distances between the Calpha atoms of the inhibitor molecules and the hydroxyl oxygen atoms of Thr-15 and Tyr-29 (1.20 and 1.60 A, respectively) clearly indicate the presence of covalent bonds between these moieties, confirming the nucleophilic role of Thr-15 during the first stage of enzymatic reactions and also indicating direct involvement of Tyr-29. The factors responsible for activating Tyr-29 remain unclear, although some structural changes around Ser-254', Asp-96, and Glu-63, common to both complexes, suggest that those residues play a function. The role of Glu-289' as the activator of Tyr-29, previously postulated for the closely related Pseudomonas 7A L-glutaminase-asparaginase, is not confirmed in this study, due to the lack of interactions between these residues in these complexes and in holoenzymes. The results reported here are consistent with previous reports that mutants of Escherichia coli L-asparaginase lacking Glu-289 remain catalytically active and prove the catalytic roles of both Thr-15 and Tyr-29, while still leaving open the question of the exact mechanism resulting in the unusual chemical properties of these residues.
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PMID:Do bacterial L-asparaginases utilize a catalytic triad Thr-Tyr-Glu? 1175 1

Serpins are key actors of systems involving proteolytic reactions, such as the haemostatic system, as they are irreversible suicide inhibitors of serine proteases. The structural flexibility and physical properties of serpins that are required for their efficient inhibitory mechanism also make them especially vulnerable to even minor factors that induce conformational changes in the native form of these molecules, leading to a number of inactive conformations, such as latent, cleaved or polymers. Increasing numbers of conformational mutations affecting haemostatic serpins, mainly antithrombin, the main endogenous anticoagulant, have been described. These mutations cause circulating deficiencies of the molecules, in most cases due to intracellular retention, which may be associated with a hyper-coagulable state. Indeed, conformational mutations in antithrombin have been identified in patients with severe venous thrombosis, which has led to the hypothesis that these disorders might be included in the group of conformational diseases. Moreover, we have recently demonstrated that other factors, including both drugs, such as the treatment with L-asparaginase, or environmental factors, such as high temperatures or hyperlipidemia, may also have conformational consequences on hepatic antithrombin, thus resulting in intracellular aggregation and plasma deficiency, which may increase the risk of thrombosis. In this study, we review the causes of deficiency of haemostatic serpins that may be explained by conformational mechanisms, and their association with an increased risk of venous thrombosis.
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PMID:Factors with conformational effects on haemostatic serpins: implications in thrombosis. 1784 43