Jul 7, 1981

Binding of porcine pancreatic phospholipase A2 to various micellar substrate analogues. Involvement of histidine-48 and aspartic acid-49 in the binding process

Biochemistry
G M Donné-Op den KelderM R Egmond

Abstract

The interaction of porcine pancreatic phospholipase A2 (PA2) with micelles of various single-chain phospholipid analogues was studied by ultraviolet absorption difference spectroscopy and light-scattering measurements. The phospholipids used were either substrate analogues or products, varying in hydrocarbon chain lengths and polar head groups. The results indicate that the enzyme forms a stable complex over a wide range of enzyme and lipid concentrations. From the equivalent "molecular weight" and from the lipid to enzyme molar ratio (N) of the micelle--enzyme complex, it can be calculated that complexes containing saturated hydrocarbon chain lipids generally consist of two enzyme molecules and half of the number of lipid monomers present in free micelles. The interaction forces between the enzyme and lipid monomers bound in the complex are mainly hydrophobic. Stronger binding is found when the essential cofactor Ca2+ is bound to the enzyme. pH-titration studies on the binding of native PA2 to aggregated lipid structures showed that at least one group with a pKA value of 6.25 is involved in the interaction with lipid micelles. At acidic pH, micelle binding is stronger than at neutral or alkaline pH. Alkylation of the active si...Continue Reading

Mentioned in this Paper

Phospholipase A2, human
lipid structure
Histidine
Enzymes, antithrombotic
Calcium
Aspartic Acid, Magnesium-Potassium (2:1:2) Salt
Structure-Activity Relationship
Complex (molecular entity)
Aggregation
Macromolecular Alteration

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