1bwr
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PROBING THE SUBSTRATE SPECIFICITY OF THE INTRACELLULAR BRAIN PLATELET-ACTIVATING FACTOR ACETYLHYDROLASE
OverviewOverview
Platelet-activating factor acetylhydrolases (PAF-AHs) are unique PLA2s, which hydrolyze the sn-2 ester linkage in PAF-like phospholipids with a, marked preference for very short acyl chains, typically acetyl. The recent, solution of the crystal structure of the alpha(1) catalytic subunit of, isoform Ib of bovine brain intracellular PAF-AH at 1.7 A resolution paved, the way for a detailed examination of the molecular basis of substrate, specificity in this enzyme. The crystal structure suggests that the side, chains of Thr103, Leu48 and Leu194 are involved in substrate recognition., Three single site mutants (L48A, T103S and L194A) were overexpressed and, their structures were solved to 2.3 A resolution or better by X-ray, diffraction methods. Enzyme kinetics showed that, compared with wild-type, protein, all three mutants have higher relative activity against, phospholipids with sn-2 acyl chains longer than an acetyl. However, for, each of the mutants we observed an unexpected and substantial reduction in, the V(max) of the reaction. These results are consistent with the model in, which residues Leu48, Thr103 and Leu194 indeed contribute to substrate, specificity and in addition suggest that the integrity of the specificity, pocket is critical for the expression of full catalytic function, thus, conferring very high substrate selectivity on the enzyme.
About this StructureAbout this Structure
1BWR is a Single protein structure of sequence from Bos taurus. Active as 1-alkyl-2-acetylglycerophosphocholine esterase, with EC number 3.1.1.47 Known structural/functional Site: . Full crystallographic information is available from OCA.
ReferenceReference
Probing the substrate specificity of the intracellular brain platelet-activating factor acetylhydrolase., Ho YS, Sheffield PJ, Masuyama J, Arai H, Li J, Aoki J, Inoue K, Derewenda U, Derewenda ZS, Protein Eng. 1999 Aug;12(8):693-700. PMID:10469831
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