General Aspects of PGs

The synthesis of PGs and relatives from membrane lipids, release of the finished products into the cytoplasm, and actions are summarized by Figure 16-5. Thus, when PG synthesis is stimulated in a cell, a fatty acid precursor, usually arachidonic acid, is released from the membrane lipids by phospholipase A2. It is acted on by the membrane PG synthetase complex, which produces a cyclic endoperoxide intermediate (Figure 16-4). This intermediate can give rise to PGE2, PGF2a, and PGI2 in cells that contain PGI2 synthetase or to TX and TXA2 in cells that contain TX synthetase (Figure 16-3). When homo-y-linolenic acid (20:3) (Figure 16-4) is the parent fatty acid, a different cyclic endoperoxide is produced. This intermediate can give rise to PGE! and PGFlu. Thus, the PGs or relatives occurring in a given cell depend on the precursor and

0 0

Post a comment