1sqm
From Proteopedia
(New page: 200px<br /> <applet load="1sqm" size="450" color="white" frame="true" align="right" spinBox="true" caption="1sqm, resolution 2.30Å" /> '''STRUCTURE OF [R563A...) |
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caption="1sqm, resolution 2.30Å" /> | caption="1sqm, resolution 2.30Å" /> | ||
'''STRUCTURE OF [R563A] LEUKOTRIENE A4 HYDROLASE'''<br /> | '''STRUCTURE OF [R563A] LEUKOTRIENE A4 HYDROLASE'''<br /> | ||
==Overview== | ==Overview== | ||
| - | Leukotriene (LT) A(4) hydrolase is a bifunctional zinc metalloenzyme, which converts LTA(4) into the neutrophil chemoattractant LTB(4) and also | + | Leukotriene (LT) A(4) hydrolase is a bifunctional zinc metalloenzyme, which converts LTA(4) into the neutrophil chemoattractant LTB(4) and also exhibits an anion-dependent aminopeptidase activity. In the x-ray crystal structure of LTA(4) hydrolase, Arg(563) and Lys(565) are found at the entrance of the active center. Here we report that replacement of Arg(563), but not Lys(565), leads to complete abrogation of the epoxide hydrolase activity. However, mutations of Arg(563) do not seem to affect substrate binding strength, because values of K(i) for LTA(4) are almost identical for wild type and (R563K)LTA(4) hydrolase. These results are supported by the 2.3-A crystal structure of (R563A)LTA(4) hydrolase, which does not reveal structural changes that can explain the complete loss of enzyme function. For the aminopeptidase reaction, mutations of Arg(563) reduce the catalytic activity (V(max) = 0.3-20%), whereas mutations of Lys(565) have limited effect on catalysis (V(max) = 58-108%). However, in (K565A)- and (K565M)LTA(4) hydrolase, i.e. mutants lacking a positive charge, values of the Michaelis constant for alanine-p-nitroanilide increase significantly (K(m) = 480-640%). Together, our data indicate that Arg(563) plays an unexpected, critical role in the epoxide hydrolase reaction, presumably in the positioning of the carboxylate tail to ensure perfect substrate alignment along the catalytic elements of the active site. In the aminopeptidase reaction, Arg(563) and Lys(565) seem to cooperate to provide sufficient binding strength and productive alignment of the substrate. In conclusion, Arg(563) and Lys(565) possess distinct roles as carboxylate recognition sites for two chemically different substrates, each of which is turned over in separate enzymatic reactions catalyzed by LTA(4) hydrolase. |
==About this Structure== | ==About this Structure== | ||
| - | 1SQM is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Homo_sapiens Homo sapiens] with ZN, YB, IMD and ACY as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Leukotriene-A(4)_hydrolase Leukotriene-A(4) hydrolase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.3.2.6 3.3.2.6] Full crystallographic information is available from [http:// | + | 1SQM is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Homo_sapiens Homo sapiens] with <scene name='pdbligand=ZN:'>ZN</scene>, <scene name='pdbligand=YB:'>YB</scene>, <scene name='pdbligand=IMD:'>IMD</scene> and <scene name='pdbligand=ACY:'>ACY</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Leukotriene-A(4)_hydrolase Leukotriene-A(4) hydrolase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.3.2.6 3.3.2.6] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1SQM OCA]. |
==Reference== | ==Reference== | ||
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[[Category: Leukotriene-A(4) hydrolase]] | [[Category: Leukotriene-A(4) hydrolase]] | ||
[[Category: Single protein]] | [[Category: Single protein]] | ||
| - | [[Category: Haeggstrom, J | + | [[Category: Haeggstrom, J Z.]] |
| - | [[Category: Rudberg, P | + | [[Category: Rudberg, P C.]] |
| - | [[Category: Tholander, F | + | [[Category: Tholander, F O.T.]] |
| - | [[Category: Thunnissen, M | + | [[Category: Thunnissen, M M.G M.]] |
[[Category: ACY]] | [[Category: ACY]] | ||
[[Category: IMD]] | [[Category: IMD]] | ||
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[[Category: epoxide hydrolase; alpha-beta protein; leukotriene biosynthesis; metalloprotease]] | [[Category: epoxide hydrolase; alpha-beta protein; leukotriene biosynthesis; metalloprotease]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 15:04:12 2008'' |
Revision as of 13:04, 21 February 2008
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STRUCTURE OF [R563A] LEUKOTRIENE A4 HYDROLASE
Overview
Leukotriene (LT) A(4) hydrolase is a bifunctional zinc metalloenzyme, which converts LTA(4) into the neutrophil chemoattractant LTB(4) and also exhibits an anion-dependent aminopeptidase activity. In the x-ray crystal structure of LTA(4) hydrolase, Arg(563) and Lys(565) are found at the entrance of the active center. Here we report that replacement of Arg(563), but not Lys(565), leads to complete abrogation of the epoxide hydrolase activity. However, mutations of Arg(563) do not seem to affect substrate binding strength, because values of K(i) for LTA(4) are almost identical for wild type and (R563K)LTA(4) hydrolase. These results are supported by the 2.3-A crystal structure of (R563A)LTA(4) hydrolase, which does not reveal structural changes that can explain the complete loss of enzyme function. For the aminopeptidase reaction, mutations of Arg(563) reduce the catalytic activity (V(max) = 0.3-20%), whereas mutations of Lys(565) have limited effect on catalysis (V(max) = 58-108%). However, in (K565A)- and (K565M)LTA(4) hydrolase, i.e. mutants lacking a positive charge, values of the Michaelis constant for alanine-p-nitroanilide increase significantly (K(m) = 480-640%). Together, our data indicate that Arg(563) plays an unexpected, critical role in the epoxide hydrolase reaction, presumably in the positioning of the carboxylate tail to ensure perfect substrate alignment along the catalytic elements of the active site. In the aminopeptidase reaction, Arg(563) and Lys(565) seem to cooperate to provide sufficient binding strength and productive alignment of the substrate. In conclusion, Arg(563) and Lys(565) possess distinct roles as carboxylate recognition sites for two chemically different substrates, each of which is turned over in separate enzymatic reactions catalyzed by LTA(4) hydrolase.
About this Structure
1SQM is a Single protein structure of sequence from Homo sapiens with , , and as ligands. Active as Leukotriene-A(4) hydrolase, with EC number 3.3.2.6 Full crystallographic information is available from OCA.
Reference
Leukotriene A4 hydrolase: identification of a common carboxylate recognition site for the epoxide hydrolase and aminopeptidase substrates., Rudberg PC, Tholander F, Andberg M, Thunnissen MM, Haeggstrom JZ, J Biol Chem. 2004 Jun 25;279(26):27376-82. Epub 2004 Apr 12. PMID:15078870
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