Endogenous activity of phospholipases A and C in Ureaplasma urealyticum

The results of recent studies support the concept that Ureaplasma urealyticum may be a major cause of perinatal infection in both term and preterm infants. It has been postulated that phospholipase degradation of placental phospholipids by microorganisms triggers the onset of premature labor. Since the presence of ureaplasmas in placentas is associated with pregnancy loss, prematurity, and neonatal morbidity, we assayed U. urealyticum for the presence of phospholipase A1, A2, and C activities. Phospholipase A1 activity was low in lysates of exponential-phase cells of U. urealyticum. Phospholipase A2 activity was present and was 100-fold higher than the activity of phospholipase A1 in serotypes 3,4, and 8. The total activity and specific activity of phospholipase A2 in serotype 8 were nearly threefold higher than the activities in serotypes 3 and 4. Cell lysates of all three serotypes showed the presence of phospholipase C activity during the exponential phase of growth, and no significant difference in activity was observed among the three serotypes. In stationary-phase cells the phospholipase C activity was 10-fold lower than the activity in exponential-phase cells. Our results demonstrate that phospholipase activities are present in U. urealyticum cells and that the specific activities of phospholipase A2 differed among the three serotypes tested, while the activities of phospholipases A1 and C were similar.