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Occurrence and Properties of Phospholipases A 1 of Plasma Membranes Prepared from Neuronal‐ and Glial‐Enriched Fractions of the Rabbit Cerebral Cortex

1981; Wiley; Volume: 36; Issue: 3 Linguagem: Inglês

10.1111/j.1471-4159.1981.tb01675.x

1471-4159

H Woelk, N. Rubly, Giuseppe Arienti, A. Gaiti, G Porcellati,

Mitochondrial Function and Pathology

Abstract: Exogenously added glycerophosphatides, specifically radioactively labelled either in the 1 or in the 2 position, were used to investigate the occurrence and properties of phospholipase A 1 in plasma membranes prepared from neuronal‐ and glial‐enriched fractions of rabbit brain. Phospholipase A 1 activity was maximal at pH values ranging between 8.0 and 9.0 for the plasma membranes of both cell types. The enzyme activity was most abundant in the microsomal fraction, with a neurondglial ratio of about 2. The plasma membranes displayed about half the enzymic activity of the microsomal fraction, whereas only small amounts of phospholipase A 1 were present in the neuronal and glial mitochondria. Investigations on the substrate specificity showed a different pattern for the enzyme of neuronal and glial origin. The release of labelled fatty acids from phosphatidylcholine by the neuronal plasma membrane phospholipase A 1 decreased with increasing degree of unsaturation of the fatty acids at the 1 position. The presence of plasmalogens and plasmalogen precursors in the incubation mixture appreciably inhibited the hydrolysis of the corresponding diacyl compounds.