title: Humicola lanuginosa lipase hydrolysis of mono-oleoyl-rac-glycerol at the lipid-water interface observed by atomic force microscopy.
abstract: A new type of planar lipid substrate for Humicola lanuginosa lipase (HLL) has been prepared by depositing a monolayer of 1-mono-oleoyl-rac-glycerol (MOG) on top of a monolayer of dipalmitoyl-phosphatidylcholine (DPPC) on mica by the Langmuir-Blodgett (LB) technique. The bilayer was subsequently exposed to HLL in a liquid cell of an atomic force microscope (AFM) allowing the time course of the lipolytic degradation to be observed. By analysing a series of AFM images, we find that enzymes are preferentially activated at the edge of nano-scale defects present in the bilayer prior to enzyme injection, while defect-free areas of the substrate are surprisingly stable towards enzyme degradation. The initial rate of hydrolysis is found to be proportional to the perimeter length, P, of the initial nano-scale defects as well as the bulk enzyme concentration, c(HLL); d(lipid)/dt=k P c(HLL). We estimate the specific rate of MOG hydrolysis by HLL to be 2.5x10(4) MOG molecules/(minute x molecule of HLL).
authors.affiliation: Department of Chemistry, Nano-Science Center, University of Copenhagen, Denmark.
authors.forename: Konstantin
authors.initials: K
authors.lastname: Balashev
authors.forename: Martin
authors.initials: M
authors.lastname: Gudmand
authors.forename: Lars
authors.initials: L
authors.lastname: Iversen
authors.forename: Thomas H
authors.initials: TH
authors.lastname: Callisen
authors.forename: Allan
authors.initials: A
authors.lastname: Svendsen
authors.forename: Thomas
authors.initials: T
authors.lastname: Bjørnholm
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000378:metabolism; D001419:Bacteria / Q000201:enzymology*; D005989:Glycerides / Q000378:metabolism*; D006868:Hydrolysis; D008049:Lipase / Q000378:metabolism*; D018625:Microscopy, Atomic Force; D014867:Water / Q000378:metabolism
chemical_list: D005989:Glycerides; D014867:Water; D015060:1,2-Dipalmitoylphosphatidylcholine; C471272:1-monooleoyl-rac-glycerol; D008049:Lipase