title: Hydrolysis of phosphatidylcholine by cerium(IV) releases significant amounts of choline and inorganic phosphate at lysosomal pH.
abstract: Niemann-Pick disease and drug-induced phospholipidosis are examples of lysosomal storage disorders in which serious respiratory infections are brought on by high levels of the phospholipid phosphatidylcholine in the acidic lamellar bodies and lysosomes of pulmonary cells. One approach to developing an effective therapeutic agent could involve the use of a metal to preferentially hydrolyze phospholipid phosphate ester bonds at mildly acidic, lysosomal pH values (~pH 4.8). Towards this end, here we have investigated phosphatidylcholine hydrolysis by twelve metal ion salts at 60°C. Using a malachite green/molybdate-based colorimetric assay to detect inorganic phosphate released upon metal-assisted phosphate ester bond hydrolysis, Ce(IV) was shown to possess outstanding reactivity in comparison to the eleven other metals. We then utilized cerium(IV) to hydrolyze phosphatidylcholine at normal, core body temperature (37°C). The malachite green/molybdate assay was used to quantitate free phosphate and an Amplex® Red-based colorimetric assay and matrix-assisted laser desorption ionization time-of-flight mass spectrometry were employed to detect choline. Ce(IV) hydrolyzed phosphatidylcholine more efficiently at lysosomal pH: i.e., at a Triton X-100:phosphatidylcholine molar mixing ratio of 1.57, yields of choline and phosphate were 51±4% and 40±4% at ~pH 4.8, compared to 28±4% and 27±5% at ~pH 7.2.
authors.affiliation: Department of Chemistry, Georgia State University, P.O. Box 4098, Atlanta, GA 30302-4098, United States. mikika18@hotmail.com
authors.forename: Miki
authors.initials: M
authors.lastname: Kassai
authors.forename: Rawin
authors.initials: R
authors.lastname: Teopipithaporn
authors.forename: Kathryn B
authors.initials: KB
authors.lastname: Grant
mesh_terms: D000818:Animals; D002563:Cerium / Q000737:chemistry*; D002642:Chick Embryo; D002794:Choline / Q000737:chemistry*; D006195:Hafnium / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D008051:Lipid Bilayers / Q000737:chemistry; D008247:Lysosomes / Q000737:chemistry*; D009566:Nitrates / Q000737:chemistry*; D017830:Octoxynol / Q000737:chemistry; D010710:Phosphates / Q000737:chemistry*; D010713:Phosphatidylcholines / Q000737:chemistry*; D015040:Zirconium / Q000737:chemistry
chemical_list: D008051:Lipid Bilayers; D009566:Nitrates; D010710:Phosphates; D010713:Phosphatidylcholines; C532772:cerium(IV) ammonium nitrate; D002563:Cerium; D017830:Octoxynol; D015040:Zirconium; D002794:Choline; D006195:Hafnium