High Phospholipase Activities in Amoebae of Dictyostelium discoideum

Amoebae of the cellular slime mold Dictyostelium discoideum exhibit high activities of particlebound phospholipase A and lysophospholipase. The activity of phospholipase A in homogenates of Dictyostelium cells was found to be 3,8 nmoles × mg protein−1× min−1 and of lysophospholipase 186 nmoles × mg protein−1× min−1. p-Chloromercuribenzoate (pCMB) and digitonin were found to be inhibitors of phospholipase A while these compounds did not influence the activity of the lysophospholipase. There was no indication that homogenates of Dictyostelium contain phospholipase C activity. The lysolecithin-acylating activity could only be detected in cell suspensions which were diluted before homogenisation to 2 mg protein/ml (2 × 107 cells/ml) probably because of the action of proteases or phospholipases in more concentrated homogenates. The results are discussed in view of the membrane activies of Dictyostelium amoebae during various morphogenetic stages.