Wheat lipase

In addition to the esterase, a wheat lipase occurs errriched in the bran. A rise in free fatty acids observable during flour storage also involves lipases from metabolism of microorganisms present in flour. 

In order to study the lipases further we have begun purification. Since the enzymes are membrane-localised, our initial experiments have been directed at solubilisation and the maintenance of stable solubilised activity. A variety of ionic and non-ionic detergents have been tested and the wheat lipase found to solubilise best with Tween 20 while for that from oat flour we use Triton X-100. In the latter case, the concentration of Triton X-100 in the assay system affects total activity. 

The solubilised oat and wheat lipases have been fractionated by ion-exchange chromatography in the presence of detergent. Two distinct lipase peaks were separated in the case of wheat extracts, both of which also contained esterase activity. Further work to characterise and purify these peaks is being undertaken. 

Unlike most enzymes, some lipases are active at very low water activities. Deterioration of wholemeal increases linearly from a level of moisture (5%), well below the range (12-14%) found in normal storage, or necessary for microbial growth ( f 16%) Previous work has shown that wheat lipase has maximal activity at a 0.8 (approx. 17% H2O). 

Recently, an interesting example of the enzymatic kinetic resolution of a-acetoxyamide 8 was demonstrated using native wheat germ lipase and immobilized lipase PS (AMANO) (Scheme 5.6). 

D-glycerol has been isolated from various red algae,377,378 rubber latex,284 turnips and rapeseed,179,294 and wheat flour.358 It is likely that this compound is a product of enzymic hydrolysis (by D-galacto-lipase)352 of DGDG. 

Muzzarelli RAA (1997) Human enzymatic activities related to the therapeutic administration of chitin derivatives. Cell Mol Life Sci 53 131-140 Muzzarelli RAA, Xia W, Tomasetti M and Ilari P (1995) Depolymerization of chitosan and substituted chitosans with the aid of a wheat germ lipase preparation. Enz Microbial Tech 17 541-545... 

Normally there is very little fat in the feces. However, fat content in stools may increase because of various fat malabsorption syndromes. Such increased fat excretion is steatorrhea. Decreased fat absorption may be the result of failure to emulsify food contents because of a deficiency in bile salts, as in liver disease or bile duct obstruction (stone or tumor). Pancreatic insufficiency may result in an inadequate pancreatic lipase supply. Finally, absorption itself may be faulty because of damage to intestinal mucosal cells through allergy or infection. An example of allergy-based malabsorption is celiac disease, which is usually associated with gluten intolerance. Gluten is a wheat protein. An example of intestinal infection is tropical sprue, which is often curable with tetracycline. Various vitamin deficiencies may accompany fat malabsorption syndromes. 

In the food industry, lipases are used in lipid modification processes. In these processes the texture, digestibility, or physical properties of natural lipids are modified by lipase-catalyzed transesterification reactions with lipids other than the original fatty acids. In the baking industry, lipases are used to influence the quality of bread through modification of the wheat flour lipids. Finally lipases are used for flavor enhancement of cheese in the dairy industry. 

In seeds, lipases may cause fat hydrolysis unless the enzymes are destroyed by heat. Palm oil produced by primitive methods in Africa used to consist of more than 10 percent of free fatty acids. Such spoilage problems are also encountered in grains and flour. The activity of lipase in wheat and other grains is highly dependent on water content. In wheat, for example, the activity of lipase is five times higher at 15.1 percent than at 8.8 percent moisture. The lipolytic activity of oats is higher than that of most other grains. 

Wheat germ lipase was purchased from the Sigma Chemical Company. 

Yet another example of the catalytic triad has been found in carboxypeptidase 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. 

Scheme 23 Lability and Stability of the C-Terminal (2-Methoxyethoxy)ethyl Ester of Glycopeptides to Lipases from Mucor javanicus and Wheat Germl ...

Lipase from wheat germ l and Upase from Aspergillus niger selectively unmasked the methyl and (2-methoxyethoxy)ethyl protected C-terminals of nucleopeptides (Scheme 25). 

The following proteins were chosen for multiple sequence alignment T. califomica acetylcholinesterase, Xanthobacter autotrophicus haloalkane dehalogenase, G. candidum lipase and wheat serine carboxypeptidase. This set was selected because they are all members of the o/fi hydrolase fold family (Ollis et al, 1992). This family of proteins, which is believed to have evolved by... 

It is well established that the same three-dimensional scaffolding in proteins often carries constellations of amino acids with diverse enzymatic functions. A classic example is the large family of a/jS, or TIM, barrel enzymes (Farber and Petsko, 1990 Lesk et ai, 1989). It appears that lipases are no exception to date five other hydrolases with similar overall tertiary folds have been identified. They are AChE from Torpedo calif arnica (Sussman et al., 1991) dienelactone hydrolase, a thiol hydrolase, from Pseudomonas sp. B13 (Pathak and Ollis, 1990 Pathak et al, 1991) haloalkane dehalogenase, with a hitherto unknown catalytic mechanism, from Xanthobacter autotrophicus (Franken et al, 1991) wheat serine carboxypeptidase II (Liao et al, 1992) and a cutinase from Fusa-rium solani (Martinez et al, 1992). Table I gives some selected physical and crystallographic data for these proteins. They all share a similar overall topology, described by Ollis et al (1992) as the a/jS hydrolase... 

CAS 9001-62-1. Any of a class of enzymes that hydrolyze fats to glycerol and fatty acids. Lipase is abundant in the pancreas but also occurs in gastric mucosa, in the small intestine, and in fatty tissue. It is found in milk, wheat germ, and various fungi. Commercial pancreatin and most trypsin preparations contain lipase. 

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