Lipases containing enzymes

Cabral and coworkers [253] have investigated the batch mode synthesis of a dipeptide acetyl phenylalanine leucinamide (AcPhe-Leu-NH2) catalyzed by a-chymotrypsin in a ceramic ultrafiltration membrane reactor using a TTAB/oc-tanol/heptane reverse micellar system. Separation of the dipeptide was achieved by selective precipitation. Later on the same group successfully synthesized the same dipeptide in the same reactor system in a continuous mode [254] with high yields (70-80%) and recovery (75-90%). The volumetric production was as high as 4.3 mmol peptide/l/day with a purity of 92%. The reactor was operated for seven days continuously without any loss of enzyme activity. Hakoda et al. [255] proposed an electro-ultrafiltration bioreactor for separation of RMs containing enzyme from the product stream. A ceramic membrane module was used to separate AOT-RMs containing lipase from isooctane. Application of an electric field enhanced the ultrafiltration efficiency (flux) and it further improved when the anode and cathode were placed in the permeate and the reten-tate side respectively. 

Since the mid-60s, the use of enzymes in detergents has been the largest of all enzyme applications. Over half of all detergents presently available contain enzymes, in particular proteases, amylases, lipases and ceUulases. Besides improved washing efficiency, the use of enzymes allows lower temperatures and shorter wash periods (of agitation) to be employed, often after a preliminary period of soaking. Further in this chapter (section 3.3) the detergent enzymes are worked out in more detail. 

Modification of nascent chylomicron particles The particle released by the intestinal mucosal cell is called a "nascent" chylomicron because it is functionally incomplete. When it reaches the plasma, the particle is rapidly modified, receiving apo E (which is recognized by hepatic receptors) and C apolipoproteins, The latter include apo C-ll, which is necessary for the activation of lipoprotein lipase, the enzyme that degrades the triacylglycerol contained in the chylomicron (see below). The source of these apolipoproteins is circulating HDL (see Figure 18.16). 

Demirkol et al. (2006) reported that the lipase of Lipozyme RM IM (Rhi-zomucor miehei) was efficient for the methanolysis of refined soybean oil with methanol to give methyl ester. RSM based on a three-level, three-factor (variable) face-centered cube design was used for the optimization of methanolysis. The independent variables contained enzyme to oil weight ratio, oil to methanol molar ratio, and reaction temperature. Critical conditions for the response at which methyl ester content of the product was 76.9% were determined. 

The human stomach and small intestine also contain enzymes that help in the hydrolysis and break-down of proteins, first into shorter chain peptides (this is done with the aid of the enzymes pepsin and trypsin), and then hydrolysed further into individual amino acids with the help of the enzyme peptidase. Any fats in food are also hydrolysed in the stomach with the aid of lipase enzyme to form fatty acids (carboxylic acids). 

A common duct from the pancreas and gall bladder enters the duodenum. Duodenal pH is 6 to 6.5 due to the presence of bicarbonate that neutralizes the acidic ch5une emptied from the stomach. The pH is optimum for enzymatic digestion of protein and peptide food. Pancreatic juice containing enzymes is secreted into the duodenum from the bile duct. Trypsin, ch5unotrypsin, and carboxypeptidase are involved in the hydrolysis of proteins into amino acids. Amylase is involved in the digestion of carbohydrates. Pancreatic lipase secretion hydrolyzes fats into fatty acids... 

Pancreatic enzyme supplements are used to treat people who lack pancreatic secretions. Pancreatm, the British Pharmacopoeia standard, is an extract of pancreas, and contains enzymes with proteinase, amylase, and lipase activity most commercial formulations are similar or identical (SEDA16, 358). 

In general terms, the crystallographic results show that lipases contain several distinct sites, each responsible for a specific function. The hydrolysis of the ester bond is accomplished by the catalytic triad, responsible for nucleophilic attack on the carbonyl carbon of the scissile ester bond, assisted by the oxyanion hole, which stabilizes the tetrahedral intermediates. The fatty acid recognition pocket defines the specificity of the leaving acid. There is also one or more interface activation sites, responsible for the conformational change in the enzyme. In this section the discussion is on the available structural data relevant to the function of all these sites. 

Enzymatic cleaners contain enzymes derived from animals, plants, or microorganisms. Plant and microorganism-derived enzymes may cause sensitization in many lens wearers (391). A list of commonly used enzymes is provided in Table 10. AU these enzymes are effective in removing deposits from the contact lens surface (392). They are biochemical catalysts that are specific for catalyzing certain chemical reactions. Those that aid in removing debris from contact lenses are protease (protein-specific enzyme), lipase (lipid-specific enzyme), and amylase (polysaccharide-specific enzyme). Such enzymes catalyze breakdown of substrate molecules— protein, lipid, and mudn— into smaller molecular units. This process yields fragments that are readily removed by mechanical force and rinsing. 

The following companies offer screening set/kits for quick enzyme selection (Table 20-2). While some companies include only industrial scale enzymes, others contain enzymes only available at lab quantities. Diversa Co. offers an enzyme subscription program for lipases, esterases, nitrilases, cellulases, glycosidases, phosphatases, and transaminases (aminotransferases). 

The optimum temp for enzyme action is between 35° and 37° at pH 5-6. Lipase contains sulfhydryl groups and is inactivated by substances that inhibit such compels. It is activated by substances that keep SH groups in the reduced state, such as glutathione, cysteine, and ascorbic acid. The addition of acid activates lipase preparations. Castor-oil lipase is activated by sulfuric, oxalic, formic, acetic and butyric acids. Acetic, salicylic and hydrochloric acids increase the action of lipase derived from various Organs of the pig. Caprylic and caproic acids increase the action of lipase derived from certain mold tungi. Almost all organic solvents decrease lipase activity, patr ether being an exception. 

Yet another example of the catalytic triad has been found in carboxy-peptidase II from wheat. The structure of this enzyme is not significantly similar to either chymotrypsin or subtilisin (Figure 9.15). This protein is a member of an intriguing family of homologous proteins that includes esterases such as acetylcholine esterase and certain lipases. These enzymes all make use of histidine-activated nucleophiles, but the nucleophiles may be cysteine rather than serine. Finally, other proteases have been discovered that contain an active-site serine or threonine residue that is activated not by a histidine-aspartate pair but by a primary amino group from the side chain of lysine or by the N-terminal amino group of the polypeptide chain. 

Probiotic bacteria have an enhanced viability and resistance to adverse environmental conditions for they are in the form of a biofilm on a phyto-carrier (Fig. 23.1). The pieparations contain enzymes cellulase, amylase, complex of proteases, lipase, as well as or nic acids, biologically active substances, vitamins, amino acids, immunoactive peptides - products of probiotics metabolism. The preparations comprise phyto-particles that are a cellulose microsoibent. 

As noted earlier, the inactivation of residual enzymes to terminate the reaction is critical to flavor stability. The heat treattnent must be adequate to inactivate the enzymes but not cause undesirable flavor changes. One should note that commercial enzyme preparations used in manufacturing may contain enzymes other than the primary enzyme(s) these are crude preparations as opposed to reagent grade enzyme preparations. For example, West [48] noted that pancreatic lipase preparations may contain amylases that can cause undesirable changes in flavor and texture in the finished product if not inactivated. 

Lipases are enzymes that specifically degrade fat. Lipases hydrolyze not just the fat on the outside of the hides and skins, but also the fat inside the skin structure. Once most of the natural fat has been removed, subsequent chemical treatments such as tanning, re-tanning and dyeing have a better effect. Lipases represent a more environmentally sound method of removing fat. For bovine hides, lipases allow tensides to be replaced completely. For sheepskins, which contain up to 40% fat, the use of solvents is... 

Many plants detoxify heavy metals by sequestering them, either as phytochelatin complexes or without specific ligands, in the vacuoles (for reviews see e.g., [73,74]). It makes sense for hyperaccumulating plants to store metal in the vacuoles as well because this organelle only contains enzymes like phosphatases, lipases, and proteinases [75] that were never identified as targets of heavy metal toxicity. Vacuole sequestration is driven to an extreme form in hyperaccumulators, where... 

We found thaf fhe cymene-Ru complex 2b displayed good activity as the racemization catalyst in ionic liquids such as [EMImjBF ([EMIm]=l-ethyl-3-methylimidazolium) and [BMImjPFg ([BMIm]=l-butyl-3-methylimidazolium) at room temperature. Thus the first DKR in ionic liquid was achieved using lipase PS-C, 2b, and trifluoroethyl acetate as the acyl donor at room temperature (Scheme 5.14 and Chart 5.11) [20]. The products were readily removed by simple extraction with ether, and the remaining ionic liquid containing enzyme and Ru catalyst was reused without further treatment for the second run. This easy recovery and recycling of reaction medium and catalysts is a big advantage of DKR in ionic liquid. 

Finally, any enzymatic process using lipases or phospholipases can be triggered at will by changing the internal balance between the core water and the free water. On the shelf, the product will contain enzymes that will be immobilized and temporarily deactivated by the bound water, and when the microemulsion is further diluted, during use, the enzymes will become free and active and the reaction will be triggered. 

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