Document Detail

A bromoenol lactone suicide substrate inactivates group VIA phospholipase A2 by generating a diffusible bromomethyl keto acid that alkylates cysteine thiols.
MedLine Citation:
PMID:  16411783     Owner:  NLM     Status:  MEDLINE    
Phospholipases A2 (PLA2) comprise a superfamily of enzymes that hydrolyze phospholipids to a free fatty acid, e.g., arachidonate, and a 2-lysophospholipid. Dissecting their individual functions has relied in large part on pharmacological inhibitors that discriminate among PLA2. Group VIA PLA2 (iPLA2beta) has a GTSTG serine lipase consensus sequence, and studies with a bromoenol lactone (BEL) suicide substrate inhibitor have been taken to suggest that iPLA2beta participates in a wide variety of biological processes. Such conclusions presume inhibitor specificity. Inhibition by BEL requires its hydrolysis by and results in uncharacterized covalent modification(s) of iPLA2beta. We performed mass spectrometric analyses of proteolytic digests of BEL-treated iPLA2beta to identify modifications associated with loss of activity. The GTSTG active site and large flanking regions of sequence are not modified by BEL treatment, but most iPLA2beta Cys residues are alkylated at various BEL concentrations to form a thioether linkage to a BEL keto acid hydrolysis product. Synthetic Cys-containing peptides are alkylated when incubated with iPLA2beta and BEL, which reflects iPLA2beta-catalyzed BEL hydrolysis to a diffusible bromomethyl keto acid product that reacts with distant thiols. The BEL concentration dependence of Cys651 alkylation closely parallels that of loss of iPLA2beta activity. No amino acid residues other than Cys were found to be modified, suggesting that Cys alkylation is the covalent modification of iPLA2beta responsible for loss of activity, and the alkylating species appears to be a diffusible hydrolysis product of BEL rather than a tethered acyl-enzyme intermediate.
Haowei Song; Sasanka Ramanadham; Shunzhong Bao; Fong-Fu Hsu; John Turk
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural    
Journal Detail:
Title:  Biochemistry     Volume:  45     ISSN:  0006-2960     ISO Abbreviation:  Biochemistry     Publication Date:  2006 Jan 
Date Detail:
Created Date:  2006-01-17     Completed Date:  2006-04-17     Revised Date:  2014-09-22    
Medline Journal Info:
Nlm Unique ID:  0370623     Medline TA:  Biochemistry     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1061-73     Citation Subset:  IM    
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MeSH Terms
Amino Acid Sequence
Baculoviridae / genetics
Cells, Cultured
Cysteine / chemistry*
Enzyme Inhibitors / chemistry,  pharmacology*
Group II Phospholipases A2
Hydrocarbons, Brominated / chemistry*
Keto Acids / chemistry*
Models, Molecular
Molecular Sequence Data
Naphthalenes / metabolism*
Phospholipases A / antagonists & inhibitors*,  chemistry,  genetics,  metabolism
Phospholipases A2
Pyrones / metabolism*
Recombinant Proteins / metabolism
Substrate Specificity
Sulfhydryl Compounds / metabolism*
Grant Support
P01-HL57278/HL/NHLBI NIH HHS; P30 DK056341/DK/NIDDK NIH HHS; P30 DK056341-05S2/DK/NIDDK NIH HHS; P30 DK056341-06/DK/NIDDK NIH HHS; P30 DK056341-069003/DK/NIDDK NIH HHS; P30-DK56341/DK/NIDDK NIH HHS; P41 RR000954/RR/NCRR NIH HHS; P41 RR000954-30/RR/NCRR NIH HHS; P41-RR00954/RR/NCRR NIH HHS; P60 DK020579/DK/NIDDK NIH HHS; P60 DK020579-269005/DK/NIDDK NIH HHS; P60-DK20579/DK/NIDDK NIH HHS; R01-69455//PHS HHS; R37 DK034388/DK/NIDDK NIH HHS; R37 DK034388-23/DK/NIDDK NIH HHS; R37-DK34388/DK/NIDDK NIH HHS
Reg. No./Substance:
0/Enzyme Inhibitors; 0/Hydrocarbons, Brominated; 0/Keto Acids; 0/Naphthalenes; 0/Pyrones; 0/Recombinant Proteins; 0/Sulfhydryl Compounds; 74-83-9/methyl bromide; 88070-98-8/6-(bromomethylene)tetrahydro-3-(1-naphthaleneyl)-2H-pyran-2-one; EC 3.1.1.-/Phospholipases A; EC II Phospholipases A2; EC A2; K848JZ4886/Cysteine

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