Phospholipase A2 activity in rat platelets]

Rat blood platelets show phospholipase A2 activities twenty times higher than human platelets. The breakdown of PE at pH 7.2 is linear for 15 minutes. There is no degradation at pH less than 5; the maximal activity is in the pH range 5.5-7.5. The presence of Ca2+ increases the phospholipase activity; an excess is not inhibitory. The optimal activity is obtained with 16 microM substrate concentration. Substrate inhibition is observed when the concentration exceeds 25 microM.