Lipase platelet-activating factor

Human milk differs from cows milk in that it contains, in addition to an LPL similar to that in cows milk, a bile salt-stimulated lipase (BSSL), which appears to have no counterpart in cows milk (Hernell and Blackberg, 1994). In addition, a third lipase known as platelet-activating factor acet-ylhydrolase activity (PAF-AH) has been demonstrated in human milk the activity is absent, or extremely low in cows milk (Furukawa, et al., 1994). 

Desymmetrization of Prochiral and wieso-Diols. Chiral 1,3-propanediol derivatives are useful building blocks for the preparation of enantiomerically pure bioactive compounds such as phospholipids [176], platelet activating factor (PAF), PAF-antagonists [177], and renin inhibitors [178]. A simple access to these syn-thons starts from 2-substituted 1,3-propanediols (Scheme 3.8). Depending on the substituent R in position 2, (/ )- or (5)-monoesters were obtained in excellent optical purities using Pseudomonas sp. lipase (PSL) [179-182]. The last three entries demonstrate an enhancement in selectivity upon lowering the reaction temperature [183]. 

Seven cyclic analogues of platelet-activating factor (PAF) have been obtained using a chemoenzymatic strategy starting from D-arabinose. This is illustrated in Scheme 14 for the C(2)-acetylated series where porcine pancreatic lipase (PPL) has been used to achieve regioselective functionalisation of diol 61M... 

The physiological function of heparin is not completely understood. It is found only in trace amounts in normal circulating blood. It exerts an antihpemic effect by releasing lipoprotein lipase from endothehal cells heparinlike proteoglycans produced by endothelial cells have anticoagulant activity. Heparin decreases platelet and inflammatory cell adhesiveness to endothelial cells, reduces the release of platelet-derived growth factor, inhibits tumor cell metastasis, and exerts an antiproliferative effect on several types of smooth muscle. 

Fig. 1. Platelet-derived growth factor (PDGF) increases phospholipase C/diglyceride lipase-mediated arachidonic acid release, stimulates PGH synthase activity, and induces de novo synthesis of this enzyme...

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