PLA2 activity in rat liver nuclei.

1. Subcellular fractions of rat liver were assayed for PLA2 activity. 2. The PLA2 assay measures the release of [3H]oleic acid from phospholipids, using labeled E. coli as substrate. 3. Nuclear fractions contained PLA2 activity, which was Ca2+ dependent and could not be explained from mitochondria, microsomal or plasma membrane contamination. 4. The Vmax value of nuclear PLA2 is 0.30 +/- 0.04 pmol oleic acid/min/mg protein; its Km value is 0.86 +/- 0.12 microM, similar to that of mitochondrial PLA2. 5. We conclude that rat liver nuclei contain PLA2 activity.