Lipase formerly

A general rule describing Burkholderia cepacia lipase (formerly called Pseudomonas cepacia lipase, PCL) catalysed conversions of primary alcohols with a chiral carbon in the / -position is depicted in Scheme 6.3. This rule, however, is only reliable if there are no oxygen substituents on the chiral carbon [14]. 

When Candida rugosa lipase (formerly named Candida cylindracea lipase) was immobilized on an epoxy-activated resin it became resistant against acetaldehyde. Due to this immunization it could be repeatedly employed for the enantioselective acylation of secondary alcohols with vinyl acetate in dry organic solvents (Scheme 2.7) [78]. 

Lipase ANL, lipase from Aspergillus niger, BCL, lipase from Burkholderia cepacia (formerly Pseudomonas cepacia) CAL-B, lipase from Candida antarctica B PPL, lipase from Pseudomonas fluorescens PPL, pig pancreatic lipase. 

A combinatorial approach for biocatalytic production of polyesters was demonstrated. A library of polyesters were synthesized in 96 deep-well plates from a combination of divinyl esters and glycols with lipases of different origin. In this screening, lipase CA was confirmed to be the most active biocatalyst for the polyester production. As acyl acceptor, 2,2,2-trifluoroethyl esters and vinyl esters were examined and the former produced the polymer of higher molecular weight. Various monomers such as carbohydrates, nucleic acids, and a natural steroid diol were used as acyl acceptor. 

Several studies have been conducted on calcium-fat interactions in human infants (64-70). Low synthesis of bile salts and low pancreatic lipase activity may be responsible for poorer fat utilization in infants than in adults (63,71). Fat from infant formulas may be lower than that from human milk because of the lack of a bile-stimulated lipase in the former (72). In infants, fat absorption tends to decrease with increase in fatty acid length, with lower degree of saturation, and with increase of total fat (3). Triglyceride structure may also influence fat absorption in the infant and, thus, indirectly, might also affect calcium absorption in the infant. 

Figure 7.10 Hormones that regulate the activity of the hormone-sensitive lipase in adipose tissue. Each hormone binds to a receptor on the outside of the plasma membrane and changes the activity of the lipase within the adipocyte, via a messenger molecule (Chapter 12). A hormone - independent lipase is also present with provides a low rate of release of fatty acid when the former is inactive.

In work concerning the directed evolution of enantioselective enzymes, there was a need for fast and efficient ways to determine the enantiomeric purity of chiral alcohols, which can be produced enzymatically either by reduction of prochiral ketones (e.g., 26) using reductases or by kinetic resolution of rac-acetates (e.g., 19) by lipases (111). In both systems, the CD approach is theoretically possible. In the former case, an LC column would have to separate the educt 26 from the product (A)/(J )-20, whereas in the latter, (5)/(J )-20 would have to be separated from (S)/(R)-19. 

In addition to cutinases, various lipases, such as from C. antarctica, Candida sp. [13, 47], Thermomyces lanuginosus [2, 14, 15, 55, 56], Burkholderia (formerly Pseudomonas) cepacia [57] and esterases from Pseudomonas sp. (serine esterase) [58] and Bacillus sp. (nitrobenzyl esterases) [59, 60], have shown PET hydrolase... 

Fatty acids of sugars are potentially useful and fully green nonionic surfactants, but the lipase-mediated esterification of carbohydrates is hampered by the low solubility of carbohydrates in reaction media that support lipase catalysis in general. Because the monoacylated product (Figure 10.8) is more soluble in traditional solvents than is the starting compound, the former tends to undergo further acylation into a diester. In contrast, the CaLB-catalyzed esterification of glucose with vinyl acetate in the ionic liquid [EMIm][BF4] was completely selective. The reaction became much faster and somewhat less selective when conducted in... 

Analysis of three lipase reactions using the titrimetric method illustrates typical reaction progress curves and how, as well as the need, to estimate initial rates by tangential analysis (Fig. C3.1.1). The corresponding initial reaction velocities were 27.5 U/mg forBurkholderia cepacia (formerly, Pseudomonas cepacia) li-... 

The natural products epothilone A and B are structurally different from taxol but have similar anticancer activity. Significantly, they have been reported to be much more active against cell lines exhibiting multiple-drug resistance [26], Taylor and co-workers at the University of Notre Dame have recently published an elegant, formal total synthesis of epothilone A [27], In this work, the authors used the CLC form of Burkholderia cepacia (formerly Pseudomonas cepacia) lipase (ChiroCLEC -PC) to resolve a key alcohol intermediate by selective acylation with vinyl acetate in /-butyl methyl ether (Fig. 6). The enantioselectivity was >20 1 at 47% conversion and efficiently provided gram quantities of the desired (R) alcohol. Since the unreacted (S) alcohol can easily be epimerized by a simple oxidation-reduction sequence and the catalyst reused without significant loss in activity, the method is ideally suited for scale-up. 

As increasing research has been carried out with these enzymes, a less empirical approach has been taken as a result of the different substrate profiles that have been compiled for various enzymes in this class. These profiles have been used to construct active site models for such versatile enzymes as the carboxylester hydrolase, pig liver esterase (PLE) (E.C. 3.1.1.1), and the microbial lipases (E.C. 3.1.1.3) from Burkholderia cepacia (formerly Pseudomonas cepacia) lipase (PCL), Candida... 

Lipase (Candida rugosa formerly Candida cylindra-cea) Produced as an off white to tan powder by controlled fermentation using Candida rugosa. Soluble in water, but practically insoluble in alcohol, in chloroform, and in ether. Major active principle lipase. Typical applications used in the hydrolysis of lipids, in the manufacture of dairy products and confectionery goods, and in the development of flavor in processed foods. 

Lipase (Aspergillus niger var.), 20 Lipase (Aspergillus oryzae var.), 20 Lipase (Candida rugosa formerly Candida cylindracea), 20 Lipase (Rhizomucor (Mucor) miehei), 20... 

Lipase [(Candida rugosa) (formerly Candida cylindracea)], 132, 787, (S3)20... 

Lipases can be divided into those that have a positional specificity and those that do not. The former preferentially hydrolyze the ester bonds of the primary ester positions. This results in the formation of mono- and diglycerides, as represented by the following reaction ... 

The major problem associated with the enzymatic acylation of sucrose is the incompatibility of the two reactants sucrose and a fatty acid ester. Sucrose is hydrophilic and readily soluble in water or polar aprotic solvents such as pyridine and dimethylformamide. The former is not a feasible solvent for (trans)esterifi-cations, for obvious thermodynamic reasons, and the latter are not suitable for the manufacture of food-grade products. The selective acylation of sucrose, as a suspension in refluxing tert-butanol, catalyzed by C. antarctica lipase B, afforded a 1 1 mixture of the 6 and 6 sucrose monoesters (Fig. 8.39) [208]. Unfortunately, the rate was too low (35% conversion in 7 days) to be commercially useful. 

Meso Compounds. Although pig liver esterase is by far the most suitable enzyme for asymmetric transformations involving meso compounds, especially diacids, there are several reports on the lipase-catalyzed hydrolysis and transesterification reactions of cyclic diol derivatives. The former includes variously substituted cycloalkene diacetates, cyclohexylidene protected erythri-tol diacetate, piperidine derivatives, and the exo-acetonide in eq 11. Complementary results are clearly demonstrated in eq 11 and eq 12 for the hydrolysis and esterification processes. 

These results give, for the first time, reliable information about the general composition of bovine juice. Its content of proteolytic enzymes is strikingly high (about 72 % of the total proteins). Chymotrypsinogen B, which was formerly considered as a minor constituent, is very abundant. On the other hand, bovine juice is quite poor in amylase and lipase. 

In RmL, 081 of Asp-203 accepts a syn-type H-bond from N81 of His-257 and an anti-type bond from Or/ of Tyr-260 (Fig. 5A). On the other hand, 082 is within a small distance of both N81 of His-257 (3.02 A) and the main-chain N of Val-205 (2.97 A). However, in the former case the angle on the hydrogen atom (082 H—Ne2) is much too acute ( 80°) for a strong H-bond. It is therefore the interaction with Val-205 that is relevant with respect to the stabilization of the side-chain conformation of Asp-203. This stereochemistry is very close to that found in chymotrypsin (Fig. 5B), where 081 of Asp-102 also accepts two H-bonds a syn type from Ne2 of His-57 and an anti from the hydroxyl of Ser-114. The overall effect is such that in lipases and in chymotrypsin the carboxyl group of the catalytic Asp is oriented in the same way with respect to the plane of the imidazole of the catalytic histidine. 

Besides cyclic esters and carbonates, six-membered cyclic depsipeptides and a five-membered cyclic phosphate were subjected to lipase-catalyzed ring-opening polymerizations, yielding poly (ester amide)s190 and polyphosphate,191 respectively. High temperatures (100—130 °C) were required for the polymerization of the former monomers. 

One of the reactions catalyzed by esterases and lipases is the reversible hydrolysis of esters (Figure 1 reaction 2). These enzymes also catalyze transesterifications and the asymmetrization of meso -substrates (Section 13.2.3.1.1). Many esterases and lipases are commercially available, making them easy to use for screening desired biotransformations without the need for culture collections and/or fermentation capabilities. As more and more research has been conducted with these enzymes, a less empirical approach is being taken due to the different substrate profiles amassed for various enzymes. These profiles have been used to construct active site models for such enzymes as pig liver esterase (PLE) (EC 3.1.1.1) and the microbial lipases (EC 3.1.1.3) Pseudomonas cepacia lipase (PCL), formerly P.fluorescens lipase, Candida rugosa lipase (CRL), formerly C. cylindracea lipase, lipase SAM-2 from Pseudomonas sp., and Rhizopus oryzae lipase (ROL) [108-116]. In addition, x-ray crystal structure information on PCL and CRL has been most helpful in predicting substrate activities and isomer preferences [117-119]. 

Nondynamic resolution processes for the production of chiral amines are based on selective N-acylation by either lipases from Burkholderia plantarii (Scheme 4.5C) or Alcaligenes faecalis penicillin G acylases (Scheme 4.5D). The former reaction is optimal with ethylmethoxyacetate as acylating agent [30 a], whereas fhe acylase is most selective with the natural substrate phenylacetic acid [30b]. 

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