Enzymatic probes of lipoprotein structure. Hydrolysis of human serum low density lipoprotein-2 by phospholipase A/sub 2/

Journal Article · Thu Jan 01 04:00:00 EST 1976 · J. Biol. Chem.; (United States)

OSTI ID:7259961

Aggerbeck, L P; Kezdy, F J; Scanu, A M

Pure phospholipase A/sub 2/ from Crotalus atrox is able to hydrolyze all the phosphatidylcholine, phosphatidylserine, and phosphatidylethanolamine of human serum low density lipoprotein (LDL/sub 2/). In accord with the substrate specificity of the enzyme, sphingomyelin, other minor lipids and proteins are not hydrolyzed. The enzyme-modified particles remain water-soluble and, upon reisolation, contain all of the lysophospholipids and free fatty acids produced during the reaction. By electron microscopic, circular dichroic, analytical ultracentrifugal, immunologic, and small angle x-ray scattering techniques, the enzyme-modified particles exhibit only modest changes when compared with native LDL/sub 2/. Accumulation of negative charges on the lipoprotein during hydrolysis results in the repression of ionization of the free fatty acid products. This electrostatic effect can be analyzed in terms of the Linderstrom-Lang model which yields an equivalent spherical radius of approximately 100 A for the particles. These results suggest that phospholipase A/sub 2/-hydrolyzable phospholipids are located at the surface of the LDL/sub 2/ particle and are in a fluid state. Hydrolysis by phospholipase A/sub 2/ causes no significant changes in the basic structural features of the particle even after the partial loss of free fatty acids and lysophospholipids to albumin. The availability of stable and well characterized LDL/sub 2/ derivatives may be useful for further studies aimed at an understanding of the mode by which proteins and lipids interact in lipoproteins.

• Research Organization: Univ. of Chicago
• OSTI ID: 7259961
• Journal Information: J. Biol. Chem.; (United States), Journal Name: J. Biol. Chem.; (United States) Vol. 251:12; ISSN JBCHA
• Country of Publication: United States
• Language: English

Related Subjects

550200* -- Biochemistry
59 BASIC BIOLOGICAL SCIENCES
ALBUMINS
BIOCHEMICAL REACTION KINETICS
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
DECOMPOSITION
ELECTRON MICROSCOPY
ENZYMES
ESTERASES
ESTERS
HYDROLASES
HYDROLYSIS
KINETICS
LIPASES
LIPIDS
LIPOPROTEINS
LYSIS
MICROSCOPY
MOLECULAR STRUCTURE
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC PHOSPHORUS COMPOUNDS
PHOSPHOLIPIDS
PROBES
PROTEINS
REACTION KINETICS
SOLVOLYSIS
SPHINGOMYELINS