Hydrolysis of phospholipids

Endothelial-anchored enzyme in multiple tissues primarily responsible for hydrolysis of phospholipids in HDL. 

Extensive studies in vitro from many groups have confirmed that exposure of LDL to a variety of pro-oxidant systems, both cell-free and cell-mediated, results in the formation of lipid hydroperoxides and peroxidation products, fragmentation of apoprotein Bioo, hydrolysis of phospholipids, oxidation of cholesterol and cholesterylesters, formation of oxysterols, preceded by consumption of a-tocopherol and accompanied by consumption of 8-carotene, the minor carotenoids and 7-tocopherol. 

Parvalbumins Phospholipase A2 High-affinity calcium buffers Hydrolysis of phospholipids with the release of free... 

Nishizuka Y (1992) Intracellular signaling by hydrolysis of phospholipids and activation of protein kinase C. Science 258 607-614... 

Fig. 1. Cleavage sites and products for the hydrolysis of phospholipids by PLD, PLC, PLA, and PLA2...

Fig. 2. Activation of an intracellular PLC by an extracellular signal (primary messenger) transduced across the membrane via a receptor and G-protein. The products DAG and IP3 that are produced by the PLC catalyzed hydrolysis of phospholipids are secondary messengers...

Several other methods, including a 31P NMR [39,40] and radiometric assay [28, 41] have also been used to monitor the PLCBc catalyzed hydrolysis of phospholipids. The assays that are currently available for PLCBc are compared in Table 1. 

Table 4. Kinetic values for the hydrolysis of phospholipids with various headgroups by PLCBc... 

Before discussing the mechanistic aspects of the PLCSc catalyzed hydrolysis of phospholipids, a brief survey of the manner in which metal ions in enzyme active sites participate in catalysis is warranted. 

Because of its unusual active site and its potential as a model for mammalian PC-PLC enzymes, there has been considerable interest in the mechanism of the PLC5c catalyzed hydrolysis of phospholipids. The few mechanistic points that are commonly accepted are that a water must be activated for attack on the phosphodiester linkage, the leaving group must be protonated, and the products must leave the enzyme active site (Fig. 11). These issues will now be examined. 

Fig. 3.14. Mechanism of the formation of a noncovalently bound tetrahedral intermediate in the hydrolysis of phospholipids by phospholipase A2 [86]... 

Since phospholipids were not soluble in water, it was necessary to emulsify them or use organic solvents for the enzymatic phospholipid hydrolyzing. Consequently, the phospholipid (phosphatidylcholine) was hydrolyzed in a two phase system of diethylether and water by a Z-modified lipase. Table I shows the hydrolysis of phospholipid by a modified lipase. 

Ryanodin receptor p56 Lck tyrosine kinase EGF receptor Cychc nucleotide phosphodiesterase Phosphohpase A2 Ribosomal protein S6 Release of Ca Activation of T cells Growth control cAMP and cGMP metabolism Hydrolysis of phospholipids Protein biosynthesis ... 

Like other arachidonate-derived endogenous compounds the endocannabinoids seem to be synthesized and released by cells on demand. The hydrolysis of phospholipid precursors, also probably embedded in the... 

In 1954, Beaufay and de Duve (27) first suggested a relationship between microsomal phospholipid and glucose-6-phosphatase. They observed a loss of enzymic activity from phospholipid-rich microsomal preparations concomitant with extraction with such organic solvents as butanol or treatment with lecithinase. Various studies were carried out to demonstrate that the latter effect was not produced through inhibition of enzymic activity by accumulated products of the hydrolysis of phospholipids. On the basis of their observations that deoxycholate treatment labilized microsomes to phospholipase action, they concluded that . . . the detergent did not exert its primary effect on the dissociation of phospholipids from microsomal protein, but that it probably disrupted... 

This chapter (9) provides advanced knowledge about phospholipases and the hydrolysis of phospholipids. 

The progressive increase of lysophospholipids within the AZ due either to SPAN PLA2 mediated hydrolysis of phospholipids, or to partition of lysophospholipids present in the bathing medium (Rigoni et al. 2005), is suggested to cause a transition from inhibition (phase 1) to promotion of neuroexocytosis (phase 2) with the mechanisms discussed here below. 

Phospholipase A2 Hydrolysis of Phospholipids Use of 31P NMR to Study the Hydrolysis, Acyl Migration, Regiospecific Synthesis, and Solubilization of Phospholipids... 

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