Lipase enzyme

The volumetric ratio of the two liquid phases (j6 = Forg/ Faq) can affect the efficiency of substrate conversion in biphasic media. The biocatalyst stability and the reaction equilibrium shift are dependent on the volume ratio of the two phases [29]. In our previous work [37], we studied the importance of the nonpolar phase in a biphasic system (octane-buffer pH 9) by varying the volume of solvent. The ratio /I = 2/10 has been the most appropriate for an improvement of the yield of the two-enzyme (lipase-lipoxygenase) system. We found that a larger volume of organic phase decreases the total yield of conversion. Nevertheless, Antonini et al. [61] affirmed that changes in the ratios of phases in water-organic two-phase system have little effect upon biotransformation rate. 

FIG. 5 Rate of hydroperoxide production in (a, ) lipoxygenation in pure aqueous medium, (b, ) lipoxygenation in biphasic system, (c, x) two-enzyme (lipase-lipoxygenase) system in two-phase medium, determined experimentally, and (d, ) modeled kinetic of the two enzyme system. (From Ref 63.)... 

Release of active pancreatic enzymes directly causes local or distant tissue damage. Trypsin digests cell membranes and leads to the activation of other pancreatic enzymes. Lipase damages fat cells, producing noxious substances that cause further pancreatic and peripancreatic injury. 

Most patients with malabsorption require pancreatic enzyme supplementation (Fig. 28-2). The combination of pancreatic enzymes (lipase, amylase, and protease) and a reduction in dietary fat (to less than 25 g/meal) enhances nutritional status and reduces steatorrhea. An initial dose containing about 30,000 international units of lipase and 10,000 international units of trypsin should be given with each meal. 

Thanks to two complementary enzymes, lipase and subtUisin, both (R)- and (S)-selechve DKR can be performed to obtain the corresponding enantiomeric products. 

One of the first fluorescence-based ee assays uses umbelliferone (14) as the built-in fluorophore and works for several different types of enzymatic reactions 70,86). In an initial investigation, the system was used to monitor the hydrolytic kinetic resolution of chiral acetates (e.g., rac-11) (Fig. 8). It is based on a sequence of two coupled enzymatic steps that converts a pair of enantiomeric alcohols formed by the asymmetric hydrolysis under study (e.g., R - and (5)-12) into a fluorescent product (e.g., 14). In the first step, (R)- and (5)-ll are subjected separately to hydrolysis in reactions catalyzed by a mutant enzyme (lipase or esterase). The goal of the assay is to measure the enantioselectivity of this kinetic resolution. The relative amount of R)- and ( S)-12 produced after a given reaction time is a measure of the enantioselectivity and can be ascertained rapidly, but not directly. 

Dietary fat consists essentially of mixed triglycerides. These fatty lipids pass through the stomach into the small intestine without much change in structure. In the small intestine, triglycerides are partly hydrolyzed by an enzyme (lipase) that leads to the formation of oil-water emulsion. 

Kim and Park subsequently reported that ruthenium pre-catalyst 2 racemizes alcohols within 30 min at room temperature [53]. However, when combined with an enzyme (lipase) in DKR at room temperature, very long reaction times (1.3 to 7 days) were required, in spite of the fact that the enzymatic KR takes only a few hours (Scheme 5.24). Despite these compatibility problems, their results constituted an important improvement, since chemoenzymatic DKR could now be performed at ambient temperature to give high yields, which enables non-thermostable enzymes to be used. More recently, we communicated a highly efficient metal- and enzyme-catalyzed DKR of alcohols at room temperature (Scheme 5.24) [40, 54]. This is the fastest DKR of alcohols hitherto reported by the combination of transition metal and enzyme catalysts. Racemization was effected by a new class of very... 

A recent development at laboratory scale is the application of an enzyme (lipase) to catalyze the hydrolysis Water and fat are mixed at low temperature (300 K) in a continuous stirred-tank reactor (CSTR). The water phase contains the enzyme. A much purer glycerol solution is obtained than in the conventional process. The disadvantage is that the equilibrium is not favorable. 

Enzyme (lipase) (fiO-substrate"" Enzyme-(fl)-substrate complex... 

Figure 6. Forward (natural) and reverse reactions catalyzed by hydrolytic enzymes, lipases...

Wong et al. (14) also studied the effect of the amount of enzyme (lipase from Candida rugosa Sigma) on monocaprin synthesis in isooctane at 37°C. They observed that monocaprin molar fraction increased when the amount of lipase was increased, but no significant increase in monocaprin yield (conversion of capric acid equal to 35%) was observed for a lipase loading of more than 100.0 mg (corresponding to 16.4% [w/w]). 

Rarely is the substituent on nitrogen modified but there are occasional examples. The racemic bicyclic ft-lactams having medium to large rings have been resolved using enzymes. Lipase PS in the presence of vinyl butanoate converted (48%) racemic r-/3-lactams 210 (n = 3) in dry acetone into resolved CM-alcohol 211 (n = 3) and the rfr-ester 212 (n = 3) with ee 97% (Equation 24). A better result was obtained for racemic cis /3-lactam 210 (n = 5 and 8) when vinyl butanoate, was replaced by 2,2,2-trifluoroethyl butanoate, but the ee for 212 ( = 5) was 82% and the ee value for 212 (n = 8) could not be determined. A similar reaction with racemic rra j-/3-lactam ( = 8) required the use of CAL-B (a lipase from C. antarctica) and vinyl butanoate, and the ee value for the tram-alcohol 213 was 85% but the value for the ester 214 could not be determined <2003TA3805>. 

In recent years, soap manufacture by an alternate route, the saponification of fatty methyl esters, has been under development, most notably in Japan (Lion Corporation) and Italy (Ballestra). The fatty methyl esters are obtained from the methanolysis of triglycerides inorganic alkali, quaternary ammonium salts, and enzymes (lipase) have been used as catalysts for methanolysis in commercially practiced processes... 

Even though the immobilized Lipase B has lew activity in acidolysis, it is quite active in ester synthesis with short-chain alcohols where it seems to be responsible for the abilities shewn by the crude enzyme. Lipase B functions almost equally well on 1-propanol and 2-propanol but for the long-chain alcohol, oleic alcohol, Lipase B has somewhat lower activity, and Lipase A seems to contribute the activity observed for the crude enzyme. 

A lipase from Arthrobacter species yielded pure (R)-HMPC at 50% hydrolysis with the smallest amount of the enzyme. Lipases from Pseudomonas fluorescens, Chromobacterium viscosum and Alcaligenes species were of less interest to us than the Arthrobacter lipase among others, judging from the optical purity of the product, degree... 

In the last few years increasing attention has been devoted to conducting bio-catalytic transformations in ionic liquids [104-107]. The first report of enzyme-(lipase-) catalyzed reactions in water-free ionic liquids dates from 2000 and involved transesterification, ammoniolysis and perhydrolysis reactions catalyzed by Candida antarctica lipase B (Fig. 7.32) [108]. 

Steatorrhoea is the formation of non-solid faeces. Floating stools, due to excess fat, are oily in appearance and foul smelling. There is increased fat excretion, which can be measured by determining the faecal fat level. Possible biological causes can be lack of bile acids (due to liver damage or hypolipidaemic drugs), defects or a reduction in pancreatic enzymes (lipase), and defective mucosal cells. The absence of bile acids will cause the faeces to turn grey or pale. 

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