Mammalian lipases

Other microbial lipases have also been successfully used in anhydrous ionic liquids, e.g., from Alcaligenes sp. (AsL) [54, 58], CaLA, Rhizomucor miehei lipase (RmL), and Thermomyces lanuginosus lipase (TIL) [54]. The lipase from pig pancreas (porcine pancreas lipase, PPL), the only mammalian lipase that has been subjected to ionic liquids, catalyzed transesterificationin[BMIm][NTf2]butnotin[BMIm][PF6]... 

Lipases are available and applied as lyophilized powders, in covalently and non-covalently immobilized form on inorganic or organic carriers, in sol-gel material 120 121 and as CLECs S4e 122l Most mammalian lipases exhibit pH optima ranging from 8 to 9 and most microbial lipases from 5.6 to 8.5. The temperature range for optimal activity is between 30 and 50 °C. In the case of labile substrates or insufficient enantiomer selectivity, hydrolysis may be carried out in water-saturated water-immiscible organic solvent such as diisopropyl ether, hexane or cyclohexane. 

Other mammalian lipases which have been studied are milk lipase (cf. Jensen, 1971). and monoacyl-glycerol lipase. The latter enzyme occurs in several tissues including intestine, liver and adipose tissue. It has high activity with monoacylglycerols when compared to diacylglycerols or triacylglycerols (see O Doherty, 1978). 

Soldatova, L., Kochoumian, L., and King, T.P., 1993, Sequence similarity of a hornet (D. maculatd) venom allergen. Phospholipase A1 with mammalian lipases. FEES Lett. 320 145-149. 

Lipases (triacyl glycerol acyl hydrolases, E.C 3.1.1.3) are a unique class of hydrolases for asymmetric synthesis86,87,S9,90e, They are available from fungi, bacteria and mammalians. The lipases most commonly used so far are the commercially supplied pig pancreas lipase (PPL)136, Pseudomonas cepacia lipase (PCL)89,137 and Candida cylindracea lipase (CCL). In most cases only the crude lipases, consisting of a mixture of proteins which may even be other hydrolases, are successfully applied1373. 

Enzymatic Hydrolysis. Enzymatic hydrolysis has received enormous attention. The enzymes generally employed are lipases from microorgan isms, plants, or mammalian liver. The great advantage of the enzymatic process is its high chemo- and stereoselectivity. 

Lipase constitutes only W of the protein in mammalian pancreatic juice. This relatively low proportion is compensated for by a very high molecular activity since one enzyme molecule can cleave neatly 7000 ester bonds per second under... 

Menon, G.K., Grayson, S., Elias, P.M. Cytochemical and biochemical localization of lipase and sphingomyelinase activity in mammalian epidermis. J. Invest. Dermatol. 86 591-597 (1986). 

Pancreatic lipase was first shown to be a selective deacylation reagent for triglycerides in 1955 (122, 123, 124, 125). Mammalian pancreatic lipase has nearly absolute (> 97% ) specificity for removal of fatty acids from the m-l,3-positions, thus making it ideal for analytical application. 

Form Supplied in usually a white or brownish powder, but also immobilized on an appropriate support. Lipases from microbial sources are virtually homogeneous in terms of hydrolytic activity, while mammalian and plant lipase preparations contain several interfering enzymes including proteases and esterases. 

Pancreatic lipase is one of the mammalian key digestive enzymes. It completes the dietary triacylglycerol breakdown initiated by preduode-nal lipases, including lingual and gastric enzymes, (see below). The enzyme is inhibited in the intestine by bile salts, but the activity is restored in the presence of colipase (CLP), a relatively short (95 residues) heat-stable polypeptide secreted by the pancreas (Semeriva and Desnuelle, 1979 Borgstrbm and Erlanson-Albertsson, 1984). The structural details of the interaction of colipase with lipase are described in Section III,C. 

Activation of lipases generates free fatty acids and lysolecithins. Lysolecithins are adsorbed within one minute by the cell wall [129], causing a reorganization of cell membrane constituents [130], recognizable by a change of the cell membrane shape [131]. Lysolecithines are reported to activate (at least in mammalian tissue) kinases [132]. 

Although PLAj activity has been detected in many mammalian tissues and cells [7-14], only a few PLAjS have been purified and cloned. Some Upases that hydrolyze triacylglycerol such as hepatic lipase and lipoprotein hpase also show PLA, activity [15]. However, these lipases will not be considered here. 

Y. Wei, J.A. Contreras, P. Sheffield, I. Osterlund, and U. Derewenda, Crystal structure of brefeldin A esterase, a bacterial homolog of the mammalian hormone-sensitive lipase, Nat. Struct. Biol., 1999, 6, 340-345. 

D. Lang, M. Rossi, and C. Pedone, A snapshot of a transition state analogue of a novel thermophilic esterase belonging to the subfamily of mammalian hormone-sensitive lipase, J. Mol. Biol., 2000, 303, 761-771. 

Other possibilities to prepare chiral cyanohydrins are the enzyme catalysed kinetic resolution of racemic cyanohydrins or cyanohydrin esters [107 and references therein], the stereospecific enzymatic esterification with vinyl acetate [108-111] (Scheme 2) and transesterification reactions with long chain alcohols [107,112]. Many reports describe the use of fipases in this area. Although the action of whole microorganisms in cyanohydrin resolution has been described [110-116],better results can be obtained by the use of isolated enzymes. Lipases from Pseudomonas sp. [107,117-119], Bacillus coagulans [110, 111], Candida cylindracea [112,119,120] as well as lipase AY [120], Lipase PS [120] and the mammalian porcine pancreatic lipase [112, 120] are known to catalyse such resolution reactions. 

Lipoproteins and Lipoprotein Lipase Cellular Uptake and Transport of Fatty Acids Intracellular Consumption of Fatty Acids Fatty Acid Synthesis in Mammalian Cells Storage of Fatty Acids in Triacylglycerol... 

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