Phospholipases classification

Phospholipases. Table 1 Classification of low molecular mass phospholipase A2 isozymes that use catalytic His... 

Six DA, Dennis EA (2000) The expanding superfamily of phospholipase A2 enzymes classification and characterization. Biochim Biophys Acta 1488 1—19... 

Serotoninergic System. Figure 1 Graphical representation of the current classification of 5-hydroxytryptamine (5-HT) receptors. Receptor subtypes represented by shaded boxes and lowercase designate receptors that have not been demonstrated to definitively function in native systems. Abbreviations 3-5r cyclic adenosine monophosphate (cAMP) phospholipase C (PLC) negative (-ve) positive (+ve)... 

Fig. 5.24 Classification of the phospholipases and the reaction of phospholipase C. a) Cleavage specificity of phospholipases Al, A2, C and D. b) Cleavage of inositol-containing phosphohpids by phospholipase C. In a reaction of particnlar importance for signal transduction, phosphohpase C (PL-C) catalyzes the cleavage of phosphatidyl inositol-4,5-bisphosphate (PtdIns(4,5)P2) into the messenger substances diacylglycerol and inositol 1,4,5-triphosphate (Ins(l,4,5)P3).

Both adrenaline and noradrenaline stimulate smooth muscles throughout the body and have a hypertensive effect. Their postsynaptic receptors are 7-helix transmembrane proteins (Fig. 11-6). A comparison of the effects of various analogs led to the classification of these receptors into classes a, a2, P, and P2, which are discussed briefly on pp. 553-555. The a receptors, which are structurally closely related to rhodopsin,753/754 are coupled via Gq /11 proteins to a phosphoinositide-activated phospholipase C (Figs. 11-9, 30-19).755 They usually provoke an excitatory response. However, in intestinal smooth muscles they are inhibitory. Adrenaline is usually more active at a receptors than is noradrenaline. A specific antagonist... 

The classification of the phospholipases, based on their site of attack, is given in Fig. 2. The phospholipases A (PLAs) are acyl hydrolases classified according to their hydrolysis of the 1-acyl ester (PLA,) or the 2-acyl ester (PLA2). Some phospholipases will hydrolyze both acyl groups and are called phospholipase B (PLB). In addition, lysophospholipases... 

S-HTj-type receptors couple positively to phospholipase C (PLC) as the principal means of conveying extracellular stimuli into intracellular responses [9]. Moreover, this type of signal transduction has become one of the hallmarks in use for classification of the S-HTj receptors [11, 12]. 

This classification is not exhaustive. Because of limited structural information, other phospholipases A2 have not yet been classified. 

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