Phospholipases B

This enzyme [EC 3.1.1.5] (also referred to as lecithinase B, lysolecithinase, and phospholipase B) catalyzes the hydrolysis of a 2-lysophosphatidylcholine to produce glycerophosphocholine and a fatty acid anion. 

PHOSPHOLIPASE A2 PHOSPHOLIPASE B PHOSPHOLIPASE C PHOSPHOLIPASE D PHOSPHOLIPID FLIP-FLOP PHOSPHOMANNOMUTASE (R)-5-Phosphomevalonate, as substrate, 5-PHOSPHOMEVALONATE KINASE 5-PHOSPHOMEVALONATE KINASE... 

Gassama-Diagne, A., Fauvel, J., and Chap, H. (1989) Purification of anew, calcium-independent, high molecular weight phospholipase A2/lysophospholipase (phospholipase B) from guinea pig intestinal brush-border membrane, J. Biol. Chem. 264, 9470-9475. 

Saito, K., Sugatani, J., and Okumura, T. (1991) Phospholipase B from Penicillium notatum, in Methods in Enzymology, Vol. 197, E. A. Dennis, editor, Academic Press, New York, pp. 446-456. 

The objective in acid degumming is to chelate the calcium and magnesium ions and render the nonhydratable phosphatide forms hydratable. In addition to phosphoric acid, citric and malic acids are effective, as well as eth-ylenediaminetetraacetic acid (EDTA). Acid-treated phosphatides are not used for production of commercial lecithins. Extensive reviews on oil degumming have been prepared.106 107 Lurgi, a German equipment manufacturer, has developed an EnzyMax process that cleaves the nonhydratable phosphatides with a phospholipase B at the triglyceride s second carbon to produce a lysophosphatide that is insoluble in oil and is removed by centrifuging.108... 

Leidich SD, Ibrahim AS, Fu Y, Koul A, Jessup C, Vitullo J, Fonzi W, Mirbod F, Nakashima S, Nozawa Y, Ghannoum MA Cloning and disruption of a caPLBl a phospholipase B gene involved in the pathogenicity of Candida albicans. J Biol Chem 1998 273 26078-26086. 

Sugiyama Y, Nakashima S, Mirbod F, Kanoh H, Kitajima Y, Ghannoum MA, Nozawa Y Molecular cloning of a second phospholipase B gene, caPLB2 from Candida albicans. Med Mycol 1999 37 61-67. 

PC can come from the diet or be synthesized in the body. Dietary PC is cleaved by a pancreatic enzyme, phospholipase B, that catalyzes hydrolysis of the fatty add from carbon-2 (C-2) of the glycerol backbone. This hydrolysis produces a free fatty add and l-acyh3-phosphocholine glycerol. The latter compound is called lysolecithin, because its parent compound PC is known as lecithin. Lysoledthin and the free fatty acid are absorbed by the enterocyte, converted back to PC, and then packaged into chylomiorons that are released into the lymphatic system. A small fraction of the choline derived from dietary PC enters the bloodstream as free choline. 

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... 

The phospholipases A, (PLAjS) comprise a large group of 1-acyl hydrolases, some of which also degrade neutral lipids (lipases) or remove the acyl group at position 2 in addition to that at position 1 (PLB), and thus must have lysophospholipase activity. Where the enzyme appears to show low selectivity for the sn-l or sn-2 position, the term phospholipase A is used. The term phospholipase B should be restricted to those enzymes where the mechanism involves minimal accumulation of lysophospholipid product. In this section, we consider various enzymes of the PLA type that do not fit a more precise definition in terms of acyl chain selectivity. 

PLA2 phospholipase A2 PLB phospholipase B PLC phospholipase C PLD phospholipase D PLs phospholipases... 

This enzyme (triacylglycerol acyl-hydrolase) has a molecular mass of approximately 42 kDa (Hide, Chan, and Li 1992) and a short half-life of about 1-3 h in dogs. Pancreatic lipase is secreted in its active form, and this activity is enhanced by colipase and bile salts the enzyme hydrolyzes triglycerides to monoglycerides. Other lipases— phospholipase a, phospholipase b, and cholesterol ester hydrolase—are also secreted by the pancreas. 

Phospholipase B C. albicans Expression of PLBl regulated as a function of morphogenetic transition 109... 

During the infection of potato leaves by Phytophthora infestans there is a rapid degradation of membrane components (chlorophyll, galactolipids, and phospholipids). We have identified an inducible phospholipase B activity which is secreted by the fungus in culture and also occurs during the infection of potato leaves. 

PA) Phospholipase B (lyso-PA) + fatty acid Fatty acids 5n-3-Glycerophosphate (GP)... 

PC) Phospholipase B choline (lyso-PC) + fatty acid Fatty acids 5/1-3-Glycerophosphorylcholine... 

The breakdown of glycerophospholipids is catalysed by a series of phospholipases designated A, B, C and D depending on their positions of attack (Fig. 11.16). In addition, phosphatidic acid phosphatase is important, but this has already been dealt with (Section 11.2.1). Two phospholipase A specificities are recognized and these are named Ai and A2 depending on the position of the ester hydrolysed in the diacylphosphoglyceride. Phospholipase B is the name usually used for an enzyme which is a... 

Phospholipase B is known as monoacylphos-pholipase (lysophospholipase). Both 1-acyl and 2-acyl monoacyl derivatives of phosphatidylcholine and phosphatidylethanolamine are attacked. Unsaturated fatty acids are the preferred chains for attack (van den Bosch et al., 1968). Other synthetic compounds are also hydrolysed e.g. acyl ethylene-glycolphosphorylcholine (Dawson, 1973). Although the classic phospholipase B is prepared from Penicillium notatum, the enzyme from that source will, in fact, hydrolyse diacylphospholipids under certain conditions, and is therefore a phospholipase A (Kawasaki and Saito, 1973). 

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