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| {{STRUCTURE_1djp| PDB=1djp | SCENE= }} | | {{STRUCTURE_1djp| PDB=1djp | SCENE= }} |
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| '''CRYSTAL STRUCTURE OF PSEUDOMONAS 7A GLUTAMINASE-ASPARAGINASE WITH THE INHIBITOR DON COVALENTLY BOUND IN THE ACTIVE SITE'''
| | ===CRYSTAL STRUCTURE OF PSEUDOMONAS 7A GLUTAMINASE-ASPARAGINASE WITH THE INHIBITOR DON COVALENTLY BOUND IN THE ACTIVE SITE=== |
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| ==Overview==
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| Pseudomonas 7A glutaminase-asparaginase (PGA) catalyzes the hydrolysis of D and L isomers of glutamine and asparagine. Crystals of PGA were reacted with diazo analogues of glutamine (6-diazo-5-oxo-L-norleucine, DON) and asparagine (5-diazo-4-oxo-L-norvaline, DONV), which are known inhibitors of the enzyme. The derivatized crystals remained isomorphous to native PGA crystals. Their structures were refined to crystallographic R = 0.20 and R(free) = 0.24 for PGA-DON and R = 0.19 and R = 0.23 for PGA-DONV. Difference Fourier electron density maps clearly showed that both DON and DONV inactivate PGA through covalent inhibition. Continuous electron density connecting the inhibitor to both Thr20 and Tyr34 of the flexible loop was observed providing strong evidence that Thr20 is the primary catalytic nucleophile and that Tyr34 plays an important role in catalysis as well. The unexpected covalent binding observed in the PGA-DON and PGA-DONV complexes shows that a secondary reaction involving the formation of a Tyr34-inhibitor bond takes place with concomitant inactivation of PGA. The predicted covalent linkage is not seen, however, suggesting an alternative method of inhibition not yet seen for these diazo analogues. These surprising results give insight as to the role of the flexible loop Thr and Tyr in the catalytic mechanism.
| | The line below this paragraph, {{ABSTRACT_PUBMED_10684596}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 10684596 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_10684596}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Pga]] | | [[Category: Pga]] |
| [[Category: Suicide inhibitor]] | | [[Category: Suicide inhibitor]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 13:55:26 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jun 30 23:10:12 2008'' |