Interfacial mechanism of phospholipase A(2): pH-dependent inhibition and Me-β-cyclodextrin activation.

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dc.contributor.authorWacklin, HPen_AU
dc.date.accessioned2009-10-22T23:29:34Zen_AU
dc.date.accessioned2010-04-30T05:04:56Zen_AU
dc.date.available2009-10-22T23:29:34Zen_AU
dc.date.available2010-04-30T05:04:56Zen_AU
dc.date.issued2009-06-30en_AU
dc.date.statistics2009-06-30en_AU
dc.description.abstractThe pH-dependent activity of phospholipase A(2) (PLA(2)) from Naja mossambica mossambica venom and the membrane-water partitioning of the lipid hydrolysis products were investigated in solid-supported palmitoyl-oleyl-phosphatidylcholine-d(31) (POPC-d(31)) membranes using neutron reflection. At pH 5, PLA(2) interacts only weakly with the substrate membrane and leads to no observable membrane breakdown, which is consistent with protonation of the catalytic histidine (His48, pK(a) similar to 6.2). The rate of the lyso-lipid partitioning into the solution phase is the same at pH 9 as at pH 7.4, and the relative membrane-water partitioning of the products is essentially the same; that is, the fatty acid accumulates in the membrane, and only the lyso-lipid is solubilized. However, Me-β-cyclodextrin (Me-β-CD) activates PLA(2) irrespective of pH by facilitating the solubilization of the lyso-lipid product, but not the fatty acid, of which only 22% is encapsulated at pH 9. Since no product solubilization is observed at pH 5 in the absence of Me-β-CD, this suggests that the hydrolytic mechanism of PLA(2) is not fully disabled at pH 5 but is inhibited by a mechanism, which is counteracted by Me-p-M-mediated release of the lyso-lipid. Me-β-CD does not interact with the substrate membrane, which indicates that at low pH the product extraction occurs directly from the enzyme active site outside the immediate membrane-water interface, whereas at pH 7-9, direct solubilization of the lyso-lipid from the membrane can also contribute to activation of PLA(2). © 2009, American Chemical Societyen_AU
dc.identifier.citationWacklin, H. P. (2009). Interfacial mechanism of phospholipase A(2): pH-dependent inhibition and Me-β-cyclodextrin activation. Biochemistry, 48(25), 5874-5881. doi:10.1021/bi802280ben_AU
dc.identifier.govdoc1323en_AU
dc.identifier.issn0006-2960en_AU
dc.identifier.issue25en_AU
dc.identifier.journaltitleBiochemistryen_AU
dc.identifier.pagination5874-5881en_AU
dc.identifier.urihttp://dx.doi.org/10.1021/bi802280ben_AU
dc.identifier.urihttp://apo.ansto.gov.au/dspace/handle/10238/2070en_AU
dc.identifier.volume48en_AU
dc.language.isoenen_AU
dc.publisherAmerican Chemical Societyen_AU
dc.subjectSolubilityen_AU
dc.subjectLipidsen_AU
dc.subjectHydrolysisen_AU
dc.subjectMembranesen_AU
dc.subjectWateren_AU
dc.subjectCarboxylic acidsen_AU
dc.titleInterfacial mechanism of phospholipase A(2): pH-dependent inhibition and Me-β-cyclodextrin activation.en_AU
dc.typeJournal Articleen_AU
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