TY - JOUR

T1 - Phospholipase A2 activity towards vesicles of DPPC and DMPC-DSPC containing small amounts of SMPC

AU - Hoyrup, Pernille

AU - Mouritsen, Ole G.

AU - Jorgensen, Kent

PY - 2001/12/1

Y1 - 2001/12/1

N2 - Phospholipase A2 (PLA2) is an interfacially active enzyme whose hydrolytic activity is known to be enhanced in one-component phospholipid bilayer substrates exhibiting dynamic micro-heterogeneity. In this study the activity of PLA2 towards large unilamellar vesicles composed of DPPC:SMPC and DMPC:DSPC:SMPC is investigated using fluorescence and HPLC techniques. Phase diagrams of the mixtures are established by differential scanning calorimetry and the PLA2 activity, monitored by the lag time, is correlated with the phase behavior of the mixtures. In addition, the degree of lipid hydrolysis in the DMPC:DSPC:SMPC lipid mixtures is detected by HPLC. The PLA2 activity is found to be significantly increased in the temperature range of the coexistence region where the lipid mixtures exhibit lateral gel-fluid phase separation. Furthermore, in the entire temperature range it is demonstrated that PLA2 preferentially hydrolyzes the short chain DMPC lipid. This discriminative effect becomes less pronounced when the asymmetric lipid SMPC is present in the lipid substrate. Inclusion of SMPC into either DPPC or DMPC:DSPC vesicles prolongs the lag time. The results clearly show that the PLA2 activity is significantly enhanced by lipid bilayer micro-heterogeneity in both one-component and multi-component lipid bilayer substrates. The PLA2 activity measurements are discussed in terms of dynamic gel-fluid lipid domain formation due to density fluctuations and static lipid domain formation due to gel-fluid phase separation.

AB - Phospholipase A2 (PLA2) is an interfacially active enzyme whose hydrolytic activity is known to be enhanced in one-component phospholipid bilayer substrates exhibiting dynamic micro-heterogeneity. In this study the activity of PLA2 towards large unilamellar vesicles composed of DPPC:SMPC and DMPC:DSPC:SMPC is investigated using fluorescence and HPLC techniques. Phase diagrams of the mixtures are established by differential scanning calorimetry and the PLA2 activity, monitored by the lag time, is correlated with the phase behavior of the mixtures. In addition, the degree of lipid hydrolysis in the DMPC:DSPC:SMPC lipid mixtures is detected by HPLC. The PLA2 activity is found to be significantly increased in the temperature range of the coexistence region where the lipid mixtures exhibit lateral gel-fluid phase separation. Furthermore, in the entire temperature range it is demonstrated that PLA2 preferentially hydrolyzes the short chain DMPC lipid. This discriminative effect becomes less pronounced when the asymmetric lipid SMPC is present in the lipid substrate. Inclusion of SMPC into either DPPC or DMPC:DSPC vesicles prolongs the lag time. The results clearly show that the PLA2 activity is significantly enhanced by lipid bilayer micro-heterogeneity in both one-component and multi-component lipid bilayer substrates. The PLA2 activity measurements are discussed in terms of dynamic gel-fluid lipid domain formation due to density fluctuations and static lipid domain formation due to gel-fluid phase separation.

KW - Fluorescence

KW - High performance liquid chromatography

KW - Interfaces

KW - Lipid bilayer

KW - Micro-heterogeneity

KW - Phase coexistence

KW - Phase separation

KW - Phospholipase A

KW - Phospholipid

UR - http://www.scopus.com/inward/record.url?scp=0035575827&partnerID=8YFLogxK

U2 - 10.1016/S0005-2736(01)00407-2

DO - 10.1016/S0005-2736(01)00407-2

M3 - Journal article

C2 - 11718669

AN - SCOPUS:0035575827

VL - 1515

SP - 133

EP - 143

JO - B B A - Biomembranes

JF - B B A - Biomembranes

SN - 0005-2736

IS - 2

ER -