title: The antibacterial properties of secreted phospholipases A2: a major physiological role for the group IIA enzyme that depends on the very high pI of the enzyme to allow penetration of the bacterial cell wall.
abstract: The antibacterial properties of human group IIA secreted phospholipase A(2) against Gram-positive bacteria as a result of membrane hydrolysis have been reported. Using Micrococcus luteus as a model system, we demonstrate the very high specificity of this human enzyme for such hydrolysis compared with the group IB, IIE, IIF, V, and X human secreted phospholipase A(2)s. A unique feature of the group IIA enzyme is its very high pI due to a large excess of cationic residues on the enzyme surface. The importance of this global positive charge in bacterial cell membrane hydrolysis and bacterial killing has been examined using charge reversal mutagenesis. The global positive charge on the enzyme surface allows penetration through the bacterial cell wall, thus allowing access of this enzyme to the cell membrane. Reduced bacterial killing was associated with the loss of positive charge and reduced cell membrane hydrolysis. All mutants were highly effective in hydrolyzing the bacterial membrane of cells in which the cell wall was permeabilized with lysozyme. These same overall characteristics were also seen with suspensions of Staphylococcus aureus and Listeria innocua, where cell membrane hydrolysis and antibacterial activity of human group IIA enzyme was also lost as a result of charge reversal mutagenesis.
authors.affiliation: Division of Biochemistry and Molecular Biology, School of Biological Sciences, University of Southampton, Bassett Crescent East, Southampton SO16 7PX, United Kingdom.
authors.forename: Stephen A
authors.initials: SA
authors.lastname: Beers
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Buckland
authors.forename: Rao S
authors.initials: RS
authors.lastname: Koduri
authors.forename: Wonhwa
authors.initials: W
authors.lastname: Cho
authors.forename: Michael H
authors.initials: MH
authors.lastname: Gelb
authors.forename: David C
authors.initials: DC
authors.lastname: Wilton
mesh_terms: D000900:Anti-Bacterial Agents / Q000378:metabolism*; D002473:Cell Wall / Q000201:enzymology / Q000378:metabolism*; D006094:Gram-Positive Bacteria / Q000254:growth & development*; D006801:Humans; D006868:Hydrolysis; D007526:Isoelectric Point; D010741:Phospholipases A / Q000502:physiology*; D021381:Protein Transport
chemical_list: D000900:Anti-Bacterial Agents; D010741:Phospholipases A