Sandbox Reserved 764: Difference between revisions
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Susanne Eschenburg, Wendy A. Shuttleworth, John V. Schloss, Nikolaus Amrhein, Jeremy N. S. Evans, Wolfgang Kabsch. Interaction of the herbicide glyphosate with its target enzyme 5-enolpyruvylshikimate 3-phosphate synthase in atomic detail : PNAS 98, 1376-1380 (13 February 2001).[DOI:10.1073/pnas.98.4.1376] </ref>. After S3P and PEP are bound to EPSP synthase, the domains undergo a conformational change into a <scene name='56/564040/Secondary_elements/2'>closed</scene> formation. Chemical modification studies on EPSPS indicate that Lysine, Arginine, and Histidine residues within this cleft are essential for activity of the enzyme. The reactive Lysine and Arginine residues in this cleft have been identified as <scene name='56/564040/Lys22/4'>Lys-22</scene> and <scene name='56/564040/Arg27/3'>Arg-27</scene> <ref>PMID:3052285</ref>. Studies suggest that both Lys-22 and Arg-27 constitute a part of the active site recognizing the anionic residues on the substrates <ref>PMID:3052285</ref>. Mutation of Lys-22 to Arg does not affect the activity of the enzyme. However, mutation of Lys-22 to either Ala or Glu leads to complete loss of enzyme activity; therefore suggesting that the cationic nature of the Lysine side chain plays an important role in the activity of EPSP synthase <ref>PMID:3052285</ref>. The following residues were also proposed to be involved in the enzyme mechanism: | Susanne Eschenburg, Wendy A. Shuttleworth, John V. Schloss, Nikolaus Amrhein, Jeremy N. S. Evans, Wolfgang Kabsch. Interaction of the herbicide glyphosate with its target enzyme 5-enolpyruvylshikimate 3-phosphate synthase in atomic detail : PNAS 98, 1376-1380 (13 February 2001).[DOI:10.1073/pnas.98.4.1376] </ref>. After S3P and PEP are bound to EPSP synthase, the domains undergo a conformational change into a <scene name='56/564040/Secondary_elements/2'>closed</scene> formation. Chemical modification studies on EPSPS indicate that Lysine, Arginine, and Histidine residues within this cleft are essential for activity of the enzyme. The reactive Lysine and Arginine residues in this cleft have been identified as <scene name='56/564040/Lys22/4'>Lys-22</scene> and <scene name='56/564040/Arg27/3'>Arg-27</scene> <ref>PMID:3052285</ref>. Studies suggest that both Lys-22 and Arg-27 constitute a part of the active site recognizing the anionic residues on the substrates <ref>PMID:3052285</ref>. Mutation of Lys-22 to Arg does not affect the activity of the enzyme. However, mutation of Lys-22 to either Ala or Glu leads to complete loss of enzyme activity; therefore suggesting that the cationic nature of the Lysine side chain plays an important role in the activity of EPSP synthase <ref>PMID:3052285</ref>. The following residues were also proposed to be involved in the enzyme mechanism: | ||
*E341 may serve as a proton donor for the C-3 of PEP. In the x-ray structure, E341 is located close to the C-2 position of PEP, and thus the carboxyl oxygen of E341 could stabilize PEP oxonium ion. <ref>PMID:3052285</ref> | |||
*His385 which is only 2.85 Å away from E341 may function as proton source for E341. <ref>PMID:3052285</ref> | |||
*K22 may act as a proton acceptor of the 5-OH of S3P which should be deprotonated to attack the C-2 of PEP (24) and interacts only with those two residues (Scheme 1). <ref>PMID:3052285</ref> | |||
*R100, D242, and D384 residues are not involved in substrate binding/catalysis, but mutagenisis results show that they are required. Therefore, it is proposed that they may play a role in domain closure or stabilize the closed conformation. <ref>PMID:3052285</ref> | |||
===Addition-Elimination Reaction=== | ===Addition-Elimination Reaction=== | ||
