Neutral lipases

Two possible pathways for the biosynthesis of 2-AG have been proposed (1) a phospholipase C (PLC) hydrolysis of membrane phospholipids followed by a second hydrolysis of the resulting 1,2-diacylglycerol by diacylglycerol lipase or (2) a phospholipase Ai (PLA,) activity that generates a lysophospholipid, which in turn is hydrolyzed to 2-AG by lysophospholipase C (Fig. 5) (Piomelli, 1998). Alternative pathways may also exist from either triacylglycerols by a neutral lipase activity or lysophosphatidic acid by a dephosphorylase. The fact that PLC and diacylglycerol lipase inhibitors inhibit 2-AG formation in cortical neurons supports the contention that 2-AG is, at least predominantly, biosynthesized by the PLC pathway (Stella, 1997). However, a mixed pathway may also be plausible. 

Hydrolysis of triacylglycerides in tissues is effected by a tissue enzyme, tri-acylglyceride lipase, which hydrolyzes triacylglycerides to glycerol and free fatty acids. There are a variety of tissue lipases that differ primarily in their optimum pH and their location in the cell. The acidic lipase is contained in lysosomes the basic lipase, in microsomes and the neutral lipase, in cytoplasm. A specific feature of the tissue lipase is its sensitivity to hormones which, by activating adenylate cyclase, elicit the transition of the inactive tissue lipase to its active... 

Structural Database of Neutral Lipases and Related Enzymes... 

Langin, D Amer, P. 2006. Importance of TNFalpha and neutral lipases in human adipose tissue lipolysis. Trends Endocrinol. Metab. 17 314—320. 

Induction of neutral lipase activity [108], i.e. triglyceride metabolism... 

Neutral lipase activity None Embryo factor (including GA ) alone induces ca. 15% activity Indole acetic acid (10 pM) +1 mM glutamine induces ca. 70 /o activity Nitrogenous compounds induce 0-55% activity [108]... 

Hills, M.J. Beevers, H. (1987a) Ca stimulated neutral lipase activity in castor bean lipid bodies. Plant Physiol. 84, 272-276. 

The neutral lipase from the lipid bodies of the endosperm from young castor bean seedlings is inhibited substantially by the addition of both oleoyl-CoA and CoA. When present alone, CoA has little detectable effect on neutral lipase activity and oleoyl-CoA causes a much lesser degree of inhibition when present on its own. 

Neutral lipase in the lipid body membranes isolated from 4 d castor seedlings was used as the enzyme in these experiments (Hills and Beevers 1987). Aliquots of lipase were incubated at 30°C for 15 min in Bis-tripropane buffer (pH 7.5) with 2.5 mM emulsified triolein, 2 mM DTT and 2 mM CaCl2. Products were extracted, separated by TLC procedures and counted for radioactivity. 

Table 1 shows that the addition of 120 pM free oleoyl-CoA and 2 mM CoA cause nearly 901 inhibition of neutral lipase activity. When present on its own, 120 pM oleoyl-CoA caused only 35 inhibition and CoA had little detectable effect on lipase activity. Fig. 1 shows the effect of oleoyl-CoA concentration in the presence of CoA, on the kinetics of oleic acid, diolein and monoolein production from triolein. After an initial inhibition at lower concentrations, there is a range of oleoyl-CoA concentrations where oleic acid release is... 

Table 1. Effect of including oleoyl-CoA and Co-A in the standard assay, on the activity of the castor bean neutral lipase.

The first step in the respiratory consumption of fats is a hydrolysis, catalysed by the enz)rme neutral lipase which results in the release of glycerol and free fatty acids. The glycerol is phosphorylated to a-glycerolphosphate, and then converted to dihydroxyacetonephos-phate, a point of entry into the EMP and pentosephosphate pathways. 

The steps in the subsequent utilization of muscle LCFAs may be summarized as follows. The free fatty acids, liberated from triglycerides by a neutral triglyceride lipase, are activated to form acyl CoAs by the mediation of LCFAcyl-CoA synthetase which is situated on the outer mitochondrial membrane. The next step involves carnitine palmitoyl transferase I (CPT I, see Figure 9) which is also located on the outer mitochondrial membrane and catalyzes the transfer of LCFAcyl residues from CoA to carnitine (y-trimethyl-amino-P-hydroxybutyrate). LCFAcyl... 

We initially tested Candida antarctica lipase using imidazolium salt as solvent because CAL was found to be the best enzyme to resolve our model substrate 5-phenyl-l-penten-3-ol (la) the acylation rate was strongly dependent on the anionic part of the solvents. The best results were recorded when [bmim][BF4] was employed as the solvent, and the reaction rate was nearly equal to that of the reference reaction in diisopropyl ether. The second choice of solvent was [bmim][PFg]. On the contrary, a significant drop in the reaction rate was obtained when the reaction was carried out in TFA salt or OTf salt. From these results, we concluded that BF4 salt and PFg salt were suitable solvents for the present lipase-catalyzed reaction. Acylation of la was accomplished by these four enzymes Candida antarctica lipase, lipase QL from Alcaligenes, Lipase PS from Burkholderia cepacia and Candida rugosa lipase. In contrast, no reaction took place when PPL or PLE was used as catalyst in this solvent system. These results were established in March 2000 but we encountered a serious problem in that the results were significantly dependent on the lot of the ILs that we prepared ourselves. The problem was very serious because sometimes the reaction did not proceed at all. So we attempted to purify the ILs and established a very successful procedure (Fig. 3) the salt was first washed with a mixed solvent of hexane and ethyl acetate (2 1 or 4 1), treated with activated charcoal and passed into activated alumina neutral type I as an acetone solution. It was evaporated and dried under reduced... 

There is no solid evidence that relates human aging and reduction of carotenoid absorption. In some studies, old people have shown a lower (3-carotene absorption than that of young people (Madani and others 1989), whereas the opposite has also been reported by other studies (Sugarman and others 1991). The absorption of lipid-soluble substances, including carotenoids, is affected by any disease related to the digestion and absorption of fats (West and Castenmiller 1998). Inadequate production of lipase and bile as well as an inadequate neutralization of the chyme in the duodenum affect carotenoid bioavailability (Guyton and Hall 2001). 

The range of values for this enzyme corresponds to 0.0 to 1.5 ml. A//20 sodium hydroxide required to neutralize the fat acids released by 1 ml. of serum under controlled conditions.18 Since 0.05 ml. of AV20 sodium hydroxide solution should be easily detectable, this corresponds to at least a 30-fold range and is in line with the large range in the blood lipids which is known to be inter-individual (p. 58). Because of lack of interest in the question, apparently no investigation has been made regarding the constancy or lack of constancy of the lipases in the blood of specific individuals. 

Saliva. The salivary glands produce a slightly alkaline secretion which—in addition to water and salts—contains glycoproteins (mucins) as lubricants, antibodies, and enzymes. a-Amylase attacks polysaccharides, and a lipase hydrolyzes a small proportion of the neutral fats. a-Amylase and lysozyme, a mu-rein-cleaving enzyme (see p. 40), probably serve to regulate the oral bacterial flora rather than for digestion (see p. 340). 

Triton X-100 has proved to be of great value in the surface dilution modeb for lipolytic enzyme action. In this experimental strategy, the surface concentration of phospholipid in mixed micelles is reduced by the addition of Triton as a neutral diluent, thereby increasing the average distance between phospholipids. This allows one to draw mechanistic inferences about the binding interactions of lipases and phospholipases with their lipid sub-stratesb... 

The oxyanion hole geometry of three complexes is visuahzed in Figures 4.2. 4. Figure 4.2 displays the active site of trypsin complexed with a peptide inhibitor [41]. In Figure 4.3, the active site of chymotrypsin complexed with a neutral aldehyde adduct is displayed [43], and in Figure 4.4, cutinase (a lipase) with a covalently bound phosphate, a transition state analog is depicted [63]. 

The plasma lipoproteins include chylomicrons, very-low-density lipoproteins (VLDL), low-density lipoproteins (LDL), and high-density lipoproteins (HDL). They function to keep lipids (primarily triacylglyc-erol and cholesteryl esters) soluble as they transport them between tissues. Lipoproteins are composed of a neutral lipid core (containing triacylglycerol, cholesteryl esters, or both) surrounded by a shell of amphipathic apolipoproteins, phospholipid, and nonesterified cholesterol. Chylomicrons are assembled in intestinal mucosal cells from dietary lipids (primarily, triacylglycerol) plus additional lipids synthesized in these cells. Each nascent chylomicron particle has one molecule of apolipoprotein B-48 (apo B-48). They are released from the cells into the lymphatic system and travel to the blood, where they receive apo C-ll and apo E from HDLs, thus making the chylomicrons functional. Apo C-ll activates lipoprotein lipase, which degrades the... 

Transesterification, fatty acid analysis of lipids, 437, 439 Triacetin, lipase assays, 378 Triacylglycerol acylhydrolase, 371, 375, 378. See also Lipases Triacylglycerols, 432 Tributyrin, lipase assays, 378 Trichloroacetic acid (TCA) solubility index for protein hydrolysis, 152 in TBARS determination, 548-550 Trienes, conjugated, determination of, 515-517, 523-524, 526, 528 Trifluoroacetic acid (TFA), for determination of neutral sugars, 721-722, 724-725, 729-730... 

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