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| - | [[Image:1sqm.gif|left|200px]] | + | {{Seed}} |
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| | {{STRUCTURE_1sqm| PDB=1sqm | SCENE= }} | | {{STRUCTURE_1sqm| PDB=1sqm | SCENE= }} |
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| - | '''STRUCTURE OF [R563A] LEUKOTRIENE A4 HYDROLASE'''
| + | ===STRUCTURE OF [R563A] LEUKOTRIENE A4 HYDROLASE=== |
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| - | ==Overview==
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| - | 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.
| + | The line below this paragraph, {{ABSTRACT_PUBMED_15078870}}, adds the Publication Abstract to the page |
| | + | (as it appears on PubMed at http://www.pubmed.gov), where 15078870 is the PubMed ID number. |
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| | + | {{ABSTRACT_PUBMED_15078870}} |
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| | ==About this Structure== | | ==About this Structure== |
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| | [[Category: Leukotriene biosynthesis]] | | [[Category: Leukotriene biosynthesis]] |
| | [[Category: Metalloprotease]] | | [[Category: Metalloprotease]] |
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 09:01:35 2008'' | + | |
| | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun Jul 27 19:21:48 2008'' |
Revision as of 16:21, 27 July 2008
Template:STRUCTURE 1sqm
STRUCTURE OF [R563A] LEUKOTRIENE A4 HYDROLASE
Template:ABSTRACT PUBMED 15078870
About this Structure
1SQM is a Single protein structure of sequence from Homo sapiens. 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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