Faculty Collaboration Database

On the substrate specificity of rat liver phospholipase A1. J Biol Chem 1988 Feb 05;263(4):1920-8

Date

02/05/1988

Pubmed ID

3338998

Scopus ID

2-s2.0-0023884060 (requires institutional sign-in at Scopus site)   40 Citations

Abstract

The substrate specificity of purified phospholipase A1 was studied using mixed micelles of phospholipid and Triton X-100. The kinetic analysis employed determined Vmax, Ks (a dissociation constant for the phospholipase A1-mixed micelle complex), and Km (the Michaelis constant for the catalytic step which reflects the binding of the enzyme to the substrate in the interface). The order of Vmax values was phosphatidic acid greater than phosphatidylethanolamine greater than phosphatidylcholine greater than phosphatidylserine. The order of Ks values was phosphatidylcholine greater than phosphatidylethanolamine greater than phosphatidic acid greater than phosphatidylserine; the order of Km values was phosphatidic acid greater than phosphatidylethanolamine = phosphatidylserine greater than phosphatidylcholine. When present together, phosphatidylcholine inhibited the hydrolysis of phosphatidylethanolamine but phosphatidylethanolamine did not affect the hydrolysis of phosphatidylcholine. Sphingomyelin, phosphatidylcholine plasmalogen, and phosphatidylethanolamine plasmalogen had no effect on the hydrolysis of phosphatidylethanolamine. The effects of the reaction products, lysolipids and/or fatty acids, were also considered for their influence on phosphatidylethanolamine hydrolysis catalyzed by phospholipase A1. Free fatty acid was found to inhibit, whereas lysophospholipids stimulated hydrolysis of phosphatidylethanolamine. In a mixture of 1,2- and 1,3-diacylglycerides in mixed micelles, only the acyl chain at the sn-1 position of the 1,2 compound was hydrolyzed. Surface charge did not modulate the hydrolysis of phosphatidylcholine vesicles or mixed micelles. In conclusion, it is hypothesized that steric hindrance at position 3 of the glycerol regulates substrate binding in the active site and that an acyl group in position 1 is favored over a vinyl ether linkage for binding.

Author List

Kucera GL, Sisson PJ, Thomas MJ, Waite M

Author

Michael J. Thomas PhD Professor in the Pharmacology and Toxicology department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Animals
Kinetics
Liposomes
Liver
Micelles
Octoxynol
Phosphatidylcholines
Phosphatidylethanolamines
Phospholipases
Phospholipases A
Phospholipases A1
Polyethylene Glycols
Rabbits
Sphingomyelins
Substrate Specificity