Monitoring of phospholipid monolayer hydrolysis by phospholipase A2 by use of polarization-modulated Fourier transform infrared spectroscopy.
Polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS) was used to follow the hydrolysis of phospholipid monolayers at the air-water interface by phospholipase A2 (PLA2). The decrease in the intensity of the nuC=O ester band of dipalmitoylphosphatidylcholine at 1733 cm(-1) and the appearance of two new infrared bands in the 1530-1580 cm(-1) region allowed to monitor phospholipid hydrolysis by PLA2. Indeed, the decrease in the intensity of the band at 1733 cm(-1) was attributed to the enzymatic hydrolysis of the acyl ester linkage of the sn-2 fatty acid on the glycerol backbone whereas the doublet appearing at 1537 and 1575 cm(-1) was attributed to the nu(a) COO- vibration of the newly formed calcium-palmitate. The presence of this band as a doublet indicates the formation of a crystalline-like calcium-palmitate monolayer. This observation supports our previously postulated mechanism for the formation of PLA2 domains at the air-water interface. Definitive assignment of the infrared bands has been possible by measuring PM-IRRAS spectra of the individual hydrolysis products (palmitic acid and lysopalmitoylphosphatidylcholine) as well as of 1-caproyl-2-palmitoyl-phosphatidylcholine and 1-palmitoyl-2-caproylphosphatidylcholine monolayers before and after hydrolysis by PLA2.
Grandbois
M
M
GREIB, Département de Chimie-Biologie, Université du Québec à Trois-Rivières, Canada.
Desbat
B
B
Salesse
C
C
D006868:Hydrolysis; D010713:Phosphatidylcholines / Q000737:chemistry* / Q000378:metabolism; D010741:Phospholipases A / Q000378:metabolism*; D054467:Phospholipases A2; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods*
D010713:Phosphatidylcholines; D010741:Phospholipases A; D054467:Phospholipases A2