Lipases surface functionalization

Alternatively, surface hydrolysis of PET can be achieved by treatment with enzymes that introduce polar groups to the polymer surface. A number of hydrolytic enzymes, such as lipases, cutinases, and esterases, have shown potential for surface functionalization of PET [36, 99]. The biocatalytic method can be performed under mild reaction conditions avoiding the use of large amounts of chemicals and energy for the finishing and dyeing processes. The enzymatic modifications are specific and can be limited to the polymer surface. Consequently, the bulk properties and mechanical stability of the polymer are not compromised, and material savings and products of better quality or with new functionalities can be obtained. 

In this communication a study of the catalytic behavior of the immobilized Rhizomucor miehei lipase in the transesterification reaction to biodiesel production has been reported. The main drawbacks associated to the current biodiesel production by basic homogeneous catalysis could be overcome by using immobilized lipases. Immobilization by adsorption and entrapment have been used as methods to prepare the heterogeneous biocatalyst. Zeolites and related materials have been used as inorganic lipase supports. To promote the enzyme adsorption, the surface of the supports have been functionalized by synthesis procedures or by post-treatments. While, the enzyme entrapping procedure has been carried out by sol-gel method in order to obtain the biocatalyst protected by a mesoporous matrix and to reduce its leaching after several catalytic uses. 

In the first approach, a maleimide-functionalized polystyrene of 40 repeat units (P DI = 1.04) was covalently coupled to the sulfur atom of a reduced disulfide bridge on the surface of the lipase B from Candida antarctica (CALB) (Figure 6.11a) [33]. TEM studies of the reaction mixture in water/THF revealed well-defined enzyme fibers with a length of several micrometers. The fibers consisted of bundles of rods, of which the smallest had diameters between 25 and 30 nm. These diameters were in... 

The efLciency ofthe lipases is dependent on the exposed surface area dictated by the number of droplets and their size in fat emulsions (Turnberg and Riley, 1985 Norkskog et al., 2001 Mu and Usy, 2004). This is one reason for the emphasis on dispersibility of lipid-based formulations as a measure of performance. Lipase activity is also a function ofthe acyl chain lengths, with LCTs hydrolyzed at a slower rate than MCTs (Mu and Usy, 2004). Furthermore, the lipases can be inhibited... 

Zeolite membranes are amenable by surface modification with a variety of chemical functional groups using simple silane chemistry, which may provide alternative surface chemistry pathways for enzyme immobilization. In this context, Shukla et al. [238] have recently used a chemically modified zeolite-clay composite membrane for the immobilization of porcine lipase using glutaraldehyde to provide a chemical linkage between the enzyme and the membrane. The effects of pH, temperature, and solvent on the performance of such biphasic zeohte-membrane reactors have been evaluated in the hydrolysis of olive oil to fatty acids. 

It is, however, the role of colipase, a cofactor unique to the pancreatic enzyme, that is of particular significance. CLP was originally believed to function by anchoring the lipase molecule to the bile salt-covered surface of the lipid micelle (Canioni et al., 1977 Verger et al., 1977), thereby playing a key role in the interfacial activation. The enhancement of activity of hPL in the presence of CLP is approximately 10-fold. Abousalham et al. (1992) used limited proteolytic degradation of pancreatic lipases by chymotrypsin as a tool to obtain information re-... 

Muscarinic receptors are glycoproteins with molecular weights of approximately 80,000. They are located on the outer surface of the cell membrane, and they are of the G-protein-linked type M, Mg, and Mg receptors couple with proteins to stimulate phospho-lipase-C, whereas Mg and M4 receptors couple with Gi proteins to inhibit adenylate cyclase (25). The molecular basis of muscarinic receptor function has been reviewed (26). Nordvall and Hacksell (27) proposed a molecular model of the transmembrane domains of the receptor, to explain the three-dimensional interaction of the receptor with its ligands. However, the authors specified that the model is "primarily of qualitative value". 

Fig. 8.9 Current working model of endothelial lipase function. EL is synthesized by endothelial cells in variety of various tissues, is secreted and binds to HSPGs on the cell surface. There it binds to circulating lipoproteins, hydrolyzing phospholipids and resulting in lipoprotein particles that are reduced in phos-...

As indicated in Fig. 9.20, lipase activities were measured as a function of the orlistat surface molar fraction. With aU lipases tested, the hydrolysis of dicaprin decreased sharply as the surface molar fraction of orlistat increased. The surface molar fractions of orlistat, which reduces lipase activity to 50% (uso), are 0.013%, 0.025% and 0.25% with PPL, RGL and HGL, respectively (Fig. 9.20 A) and 0.00025% with HPL (Fig. 9.20B). On the one hand, it should be remembered that the turnover rates of gastric and pancreatic lipases are quite different [115]. Consequently, the amounts of each hpase injected into the reaction compartment of the zero-order trough were different (see legend of Fig. 9.20), leading to various orh-stat/hpase molar ratios. On the other hand, we know that monolayer systems are characterized by a low specific surface (around 1 cm /cm ). As a consequence, only a small fraction of the injected enzyme is bound to the monomolecular film. 

Inhibition of Pancreatic Lipase on Oil Drop Pre-poisoned with Orlistat Tiss et al. [117] studied the partitioning of orhstat between the core and the surface of an oil drop, as a function of the orhstat concentration in the oil. The molar fraction of orhstat at the oil drop surface was eshmated using the Gibbs surface excess equation. With these data it becomes possible to express orhstat con-... 

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