NONCOMPETITIVE INHIBITION OF PHOSPHOLIPASE A(2) ACTIVITY BY MAGNESIUM

Magnesium (Mg2+) has a multitude of physiological effects. A new appro ach in the therapy of acute asthma is the use of intravenous and/or ae rosolized Mg2+ as bronchodilatator. Asthma has also an inflammatory co mponent, dependent among other things on the phospholipase A(2) (PLA(2 )) activity. Purpose of this study was to quantify the inhibitory effe ct of Mg2+ on the PLA(2) activity in an in vitro model and to describe the mechanism of inhibition. PLA(2) was incubated with different subs trate concentrations and either buffer or Mg2+. The activity was measu red in a radioactive assay. Lineweaver-Burk representation of the data was used to determine the type of inhibition. Mg2+ inhibits statistic ally significantly the PLA(2) activity (p less than or equal to 0.01). After Mg2+-exposure Vmax is decreased. The inhibition is noncompetiti ve. K-1 = 3.25 mM.