SUBCELLULAR DISTRIBUTION OF LYSOPHOSPHOLIPASE IN BOVINE ADRENAL MEDULLA

A study was made of lysophospholipase activity in bovine adrenal medulla. Maximum hydrolysis of lysolecithin was obtained at pH 6.5. The activity of the enzyme was 5.8 μmole × g tissue−1× hour−1. Differential centrifugation showed that about 90% of the enzyme was confined to particles. 55% of the activity present in the low speed supernatant was recovered in the “large granule fraction”. About 35% sedimented with the microsomes. Density gradient centrifugation (1.3–2.0 M sucrose) of the large granule fraction revealed that lysosomes and chromaffin granules contained no significant lysophospholipase activity. By the use of a second gradient (1.0–1.6 M), mitochondria could be partly separated from the microsomes which contaminate the large granule fraction. Lysophospholipase appeared to be concentrated in dense microsomal elements. It is concluded that most, if not all, of the lysophospholipase activity in bovine adrenal medulla is localised in microsomal elements. Copyright © 1969, Wiley Blackwell. All rights reserved