| 1. |
- Adlercreutz, Patrick, et al.
(författare)
-
Enzymatic conversions of polar lipids. Principles, problems and solutions
- 2001
-
Ingår i: Journal of Molecular Catalysis - B Enzymatic. - 1381-1177. ; 11:4-6, s. 173-178
-
Forskningsöversikt (refereegranskat)abstract
- This text provides a brief overview of the principles of enzymatic lipid conversion and some recent advances in the enzymatic conversion of glycerophospholipids and galactolipids. Lipases and phospholipases are used to exchange fatty acids or the polar group in the lipids. The reactions can be carried out either as hydrolysis-esterification sequences or as one-step transferase reactions. The scope and limitations of the different methods are discussed.
|
|
| 2. |
- Fureby, Anna Millqvist, et al.
(författare)
-
Acyl group migrations in 2-monoolein
- 1996
-
Ingår i: Biocatalysis and Biotransformation. - : Informa UK Limited. - 1024-2422 .- 1029-2446. ; 14:2, s. 89-111
-
Tidskriftsartikel (refereegranskat)abstract
- Acyl migration in 2-monoolein dissolved in solvents under conditions common in lipid modification reactions has been studied. The effects on acyl migration of solvent, incubation temperature, water activity, polar additives and solid additives have been investigated. Extensive acyl migration occured in aliphatic hydrocarbons and water-miscible alcohols under dry conditions. The acyl migration rate could be decreased in several nonpolar solvents by adding a small amount of water or an alcohol. Increasing water activity had no effect in isooctane, but decreased the acyl migration rate dramatically in methyl tert-butyl ether and methyl isobutyl ketone. Several commonly used enzyme supports catalysed acyl migration, showing that supports with surface charges could catalyse acyl migration.
|
|
| 3. |
|
|
| 4. |
- Virto, Carmen, et al.
(författare)
-
Candida antarctica lipase B-catalysed synthesis of dihydroxyacetone fatty acid esters
- 2000
-
Ingår i: Biocatalysis and Biotransformation. - : Informa UK Limited. - 1024-2422 .- 1029-2446. ; 18:1, s. 13-29
-
Tidskriftsartikel (refereegranskat)abstract
- The enzymatic syntheses of 1-lauroyl-dihydroxyacetone and 1,3-dilauroyl-dihydroxyacetone were investigated. Lipase B from Candida antarctica (SP435) was used to catalyse the acylation of dihydroxyacetone (DHA) with lauric acid in organic solvent media at controlled water activity. High conversions of dihydroxyacetone (> 90%) are achieved when the water activity is 0.11 or below in solvents of various hydrophobicities, such as diethyl ether, methyl-tert-butyl ether (MTBE) and diphenyl ether. The main product in the esterification of DHA with lauric acid is 1-lauroyl-DHA, while the amount of 1,3-dilauroyl-DHA that is produced can be increased by changing the reaction conditions. Thus, decreasing the water activity from 0.75 to 0.06 resulted in an increase in the total yield of 1,3-dilauroyl-DHA from 3% to 20%. Solvents which have high log P values favoured the acylation of 1-lauroyl-DHA and thereby the formation of 1,3-dilauroyl-DHA. Thus, when diphenyl ether was used in this reaction, the yield of 1,3-dilauroyl-DHA was 45%. Complete acylation to 1,3-dilauroyl-DHA was achieved when a fatty acid vinyl ester was used as acyl donor in a closed reactor.
|
|
| 5. |
- Virto, Carmen, et al.
(författare)
-
Catalytic activity of noncovalent complexes of horse liver alcohol dehydrogenase, NAD+ and polymers, dissolved or suspended in organic solvents
- 1995
-
Ingår i: Biotechnology Letters. - 0141-5492. ; 17:8, s. 877-882
-
Tidskriftsartikel (refereegranskat)abstract
- Noncovalent complexes were formed by lyophilization of aqueous solutions containing horse liver alcohol dehydrogenase, NAD+ and a polymer [ethyl cellulose or poly(vinyl butyral)]. The complexes expressed higher specific catalytic activity in organic solvents as compared to a corresponding amount of enzyme deposited on to Celite or lyophilized enzyme powder. The noncovalent complexes were soluble in toluene. In butyl acetate and methyl t-butyl ether, suspensions of fine particles were formed.
|
|
| 6. |
- Virto, Carmen, et al.
(författare)
-
Enzymatic synthesis of lysophosphatidic acid and phosphatidic acid
- 1999
-
Ingår i: Enzyme and Microbial Technology. - 0141-0229. ; 24:10, s. 651-658
-
Tidskriftsartikel (refereegranskat)abstract
- Immobilised 1,3-specific lipase from Rhizopus arrhizus was used as catalyst for the esterification of dl-glycero-3-phosphate and fatty acid or fatty acid vinyl ester in a solvent-free system. With lauric acid vinyl ester as acyl donor, a(w)<0.53 favored the synthesis of lysophosphatidic acid (1-acyl-rac-glycero-3-phosphate, LPA1) and the spontaneous acyl migration of the fatty acid on the molecule. Subsequent acylation by the enzyme resulted in high phosphatidic acid (1,2-diacyl-rac-glycero-3-phosphate, PA) formation and high total conversions (>95%). With oleic acid, maximum conversions of 55% were obtained at low water activities. Temperatures below melting point of the product favored precipitation and resulted in high final conversion and high product ratio [LPA/(PA+LPA)]. Thus, LPA was the only product with lauric acid vinyl ester as acyl donor at 25°C. Increased substrate ratio (dl-glycero-3-phosphate/fatty acid) from 0.05 to 1 resulted in a higher ratio of LPA to PA formed, but a lower total conversion of dl-glycero-3-phosphate. Increased amounts of enzyme preparation did not result in higher esterification rates, probably due to high mass-transfer limitations. Copyright (C) 1999 Elsevier Science Inc. All rights reserved.
|
|
| 7. |
- Virto, Carmen, et al.
(författare)
-
Hydrolytic and transphosphatidylation activities of phospholipase D from Savoy cabbage towards lysophosphatidylcholine
- 2000
-
Ingår i: Chemistry and Physics of Lipids. - 0009-3084. ; 106:1, s. 41-51
-
Tidskriftsartikel (refereegranskat)abstract
- The hydrolysis and transphosphatidylation of lysophosphatidylcholine (LPC), with a partially purified preparation of phospholipase D (PL D) from Savoy cabbage, was investigated. These reactions were about 20 times slower than the hydrolysis of phosphatidylcholine (PC) in a micellar system. For the transfer reaction, 2 M glycerol was included in the media, which suppressed the hydrolytic reaction. Both reactions presented similar V(max) values, suggesting that the formation of the phosphatidyl-enzyme intermediate is the rate-limiting step. The enzyme had an absolute requirement for Ca2+, and the optimum concentration was approximately 40 mM CaCl2. K(Ca)(app) was calculated to be 8.6±0.74 mM for the hydrolytic and 10±0.97 mM for the transphosphatidylation reaction. Both activities reached a maximum at pH 5.5, independent of Ca2+ concentration. Kinetic studies showed that the Km(app) for the glycerol in the transphosphatidylation reaction is 388±37 mM. Km(app) for the lysophosphatidylcholine depended on Ca2+ concentration and fell between 1 and 3 mM at CaCl2 concentrations from 4 to 40 mM. SDS, TX-100, and CTAB did not activate the enzyme as reported for phosphatidylcholine hydrolysis; on the contrary, reaction rates decreased at detergent concentrations at or above that of lysophosphatidylcholine. Copyright (C) 2000 Elsevier Science Ireland Ltd.
|
|
| 8. |
- Virto, Carmen
(författare)
-
LIPASES AND PHOSPHOLIPASES IN PHOSPHOLIPID SYNTHESIS
- 1999
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The synthesis of phospholipids with defined fatty acid and polar head composition catalysed by lipases and phospholipases was investigated. Lipases from Rhizopus arrhizus and Candida antarctica were used for the direct acylation of DL-a-glycerophosphate and L-a-glycerophosphatidylcholine, with different fatty acids. Esterification reactions can be carried out in systems with low water activity, in which the equilibrium is favoured towards synthesis, and hydrolysis is minimised. For optimisation of the processes, it is important to consider various reaction parameters, principally the water content of the media. In the acylation of glycerophosphate and glycerophosphorylcholine, fatty acid vinyl esters gave better yields (>95%) than free fatty acid, in the formation of lysophosphatidic acid and phosphatidic acid or lysophosphatidylcholine and phosphatidylcholine. Solvent free systems were chosen for both reactions, but in some cases conversions could be easily improved by the addition of a small amount of solvent, such as t-butanol. The choline polar head group of lysophosphatidylcholine was exchanged with glycerol in a reaction catalysed by a phospholipase D from Savoy cabbage, in an aqueous micellar system. Characterisation of this reaction and of the hydrolysis showed that both reactions are similar in their Ca2+ ion dependence, kinetic parameters and pH optima. Contrary to the action of the enzyme towards phosphatidylcholine, phospholipase D does not need detergents or solvents to display optimum activity, with lysophosphatidylcholine as substrate. A combination of two phospholipases was used for the formation of lysophosphatidic acid and the analogue, 1-acyl-dihydroxyacetonephosphate, in diethyl ether-aqueous two-phase systems. Microbial phospholipase D from Streptomyces sp. was used in the transesterification of egg phosphatidylcholine with 1-lauroyl-glycerol or 1-lauroyl-dihydroxyacetone, to form two complex phospholipids, 1-lauroyl-phosphatidylglycerol and 1-lauroyl-phosphatidyldihydroxyacetone, respectively. The Km values for the alcohol acceptors were very low, 23±7 and 104±5 mM for 1-lauroyl-glycerol and 1-lauroyl-dihydroxyacetone, respectively. Phospholipase C from Bacillus cereus selectively hydrolysed the obtained products, giving the desired 1-acyl-glycerophosphate and 1-acyl-dihydroxyacetonephosphate in stoichiometric amounts. The facile recovery of the products from the ether phases in both PL D and PL C catalysed reactions, makes this a very attractive system. Finally, the direct esterification of dihydroxyacetone and lauric acid in solvent systems at controlled water activity is described. High yields (>90%) were easily achieved at low water activities of 0.06-0.11. The main product of this reaction was 1-lauroyl-dihydroxyacetone under most of the conditions tested, but the formation of the 1,3-dilauroyl-dihydroxyacetonephosphate could easily be increased by selection of a more hydrophobic solvent, or with the use of vinyl laurate as acyl donor. Using the latter approach, sole formation of 1,3-dilauroyl-dihydroxyacetone was achieved if the reactions were carried out in hermetically closed reactors.
|
|
| 9. |
- Virto, Carmen, et al.
(författare)
-
Lysophosphatidylcholine synthesis with Candida antarctica lipase B (Novozym 435)
- 2000
-
Ingår i: Enzyme and Microbial Technology. - 0141-0229. ; 26:8, s. 630-635
-
Tidskriftsartikel (refereegranskat)abstract
- Immobilized lipase from Candida antarctica lipase B (Novozym 435) was effective in the synthesis of lysophosphatidylcholine (LPC). The transesterification of L-α-glycerophosphorylcholine (GPC) and vinyl laurate was carried out in a solvent free system or in the presence of 50% (v/v) t- butanol. High conversions (>95%) were easily achieved. The lipase was selective for the sn-1 position of the glycerol backbone, and almost no phosphatidylcholine was produced in the first 24 hours of the reaction. However, and probably due to acyl migration, the formation of phosphatidylcholine (PC) increased slowly if the reactions were incubated over a long period of time. The synthetic reaction was only possible with a high excess of vinyl laurate over glycerophosphorylcholine (>10 times). High purity products could be produced by a decrease of the reaction temperature to induce precipitation of the product. The temperature needed depended on the fatty acid chain length. Thus, only lysophosphatidylcholine was produced with palmitic acid vinyl ester at 45°C, whereas for the vinyl esters of lauric acid, capric acid, and caprylic acid, a lower reaction temperature (25°C) was necessary to obtain solely the lysophospholipid products. (C) 2000 Elsevier Science Inc.
|
|
| 10. |
- Virto, Carmen, et al.
(författare)
-
Two-enzyme system for the synthesis of 1-lauroyl-rac-glycerophosphate (lysophosphatidic acid) and 1-lauroyl-dihydroxyacetonephosphate
- 2000
-
Ingår i: Chemistry and Physics of Lipids. - 0009-3084. ; 104:2, s. 175-184
-
Tidskriftsartikel (refereegranskat)abstract
- A combination of two enzymes, phospholipase D (PL D) and C (PL C), was investigated for the production of two lysophospholipids, 1-lauroyl-rac- glycerophosphate (1-LGP) and 1-lauroyl-dihydroxyacetonephosphate (1-LDHAP). The high transphosphatidylation ability of phospholipase D from Streptomyces sp. allowed the formation of 1-lauroyl-phosphatidylglycerol (1-LPG) and 1- lauroyl-phosphatidyldihydroxyacetone (1-LPDHA) from phosphatidylcholine (PC) and 1-monolauroyl-rac-glycerol (1-MLG) and 1-lauroyl-dihydroxyacetone (1- MDHA), respectively. A two-phase system, diethyl ether/water, was chosen for the convenience of the recovery of the water insoluble products. A similar two-phase system was used for hydrolysis of the complex phospholipids by phospholipase C form Bacillus cereus, which released both lysophospholipids. Only trace amounts of phosphatidic acid (PA) were detected showing that the enzyme is highly selective for the release of the diacylglycerol and 1- lauroyl-rac-glycerophosphate and 1-lauroyl-dihydroxyacetonephosphate.
|
|
