Rat osseous plate alkaline phosphatase as Langmuir monolayer--an infrared study at the air-water interface.
A glycosylphosphatidylinositol (GPI)-anchored enzyme (rat osseous plate alkaline phosphatase-OAP) was studied as monolayer (pure and mixed with lipids) at the air-water interface. Surface pressure and surface potential-area isotherms showed that the enzyme forms a stable monolayer and exhibits a liquid-expanded state even at surface pressure as high as 30 mN m(-1). Isotherms for mixed dimyristoylphosphatidic acid (DMPA)-OAP monolayer showed the absence of a liquid-expanded/liquid-condensed phase transition as observed for pure DMPA monolayer. In both cases, pure or mixed monolayer, the enzyme preserves its native conformation under compression at the air-water interface as observed from in situ p-polarized light Fourier transform-infrared reflection-absorption spectroscopic (FT-IRRAS) measurements. Changes in orientation and conformation of the enzyme due to the presence or absence of DMPA, as well as due to the surface compression, are discussed.
Caseli
Luciano
L
Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo, Brazil 14040-901. lcaseli@usp.br
Masui
Douglas C
DC
Furriel
Rosa P M
RP
Leone
Francisco A
FA
Zaniquelli
Maria E D
ME
Orbulescu
Jhony
J
Leblanc
Roger M
RM
D000469:Alkaline Phosphatase / Q000737:chemistry* / Q000302:isolation & purification; D000818:Animals; D020404:Glycerophospholipids / Q000737:chemistry*; D017261:Glycosylphosphatidylinositols / Q000737:chemistry* / Q000302:isolation & purification; D008567:Membranes, Artificial; D044367:Phase Transition; D051381:Rats; D013055:Spectrophotometry, Infrared
D020404:Glycerophospholipids; D017261:Glycosylphosphatidylinositols; D008567:Membranes, Artificial; C025602:dimyristoylphosphatidic acid; D000469:Alkaline Phosphatase