Triglycerids hydrolysis

In adipose tissue, insulin stimulation suppresses triglyceride hydrolysis (to free fatty acids and glycerol) by activating cAMP phosphodiesterase (cAMP PDE). Cyclic AMP, (3, 5 cAMP), is required to stimulate hormone sensitive lipase (HSL), the enzyme which hydrolyses triglyceride within adipocytes PDE converts active 3, 5 cAMP to inactive 5 AMP thus preventing the stimulation of HSL. The net effect of insulin on lipid metabolism is to promote storage. 

Biosynthesis and degradation of glycosaminoglycans biosynthesis of collagen, mineralization and demineralization of bone. Fatty acid synthesis and triglyceride storage in adipocytes promoted by insulin and triglyceride hydrolysis and fatty acid release stimulated by glucagon and adrenaline (epinephrine). 

The substrate for the LPL is the triglyceride contained within the oily core of VLDL particles and chylomicrons. The fatty acids and monoglycerides liberated from triglyceride hydrolysis are taken into the adipocytes and reformed into neutral fat for calorie storage (Figure 9.11). The ultimate result of the delipidation of VLDL and chylomicrons to the formation of low-density lipoproteins (LDL) as described in Section 5.5. 

Lipoprotein lipase (LPL) Local enzymatic Endothelial cells within adipose tissue Lipoprotein-triglyceride hydrolysis... 

The liver synthesizes VLDL to transport triglycerides, vitamin E and, to a lesser extent, cholesterol from the hepatocytes to various tissues of the body. Initially, VLDL contain apolipoprotein B-100 (apoB-100), apoE, and the C-apolipoproteins, but receive additional apolipoproteins and cholesterol esters from HDL in the circulation. Following triglyceride hydrolysis by LPL, VLDL remnants, termed IDL, are formed... 

On completion of the two pre-incubation steps, 10 pi of the preincubated sample will be added to 500 pi of the preincubated emulsion in triplicate, and the LPL-cata-lyzed triglyceride hydrolysis will be allowed to proceed for 1 h at 28°C. The reaction is stopped by adding 5.33 ml of methanol chloroform heptane (56 50 4 by volume) and vigorous shaking. 

The dedd cells of the mycelium of Rhizopus arrhizus constitute d naturally immobilized lipdse very active in organic solvents. This immobilized enzyme was used for hydrolysis and synthesis of ester bonds triglycerides hydrolysis, and interesterification, esters and glycerides synthesis. More recently, the catalytic system has been applied in drug synthesis to the resolution of racemic esters with a good enantioselectivity. 

Methyl-tertiobutyl-ether / acetone was found to be a good solvent of the racemic epoxy-ester, and thus is used for the reaction, as for triglycerides hydrolysis. 

Rhizopus arrhizus dead mycelium was found to be very active in organic solvents as a naturally immobilized lipase. Triglycerides hydrolysis and interesterification, esters and glycerides synthesis, natural flavour esters preparation and racemic mixtures resolution in pharmaceutical drugs synthesis are among the successfully designed processes, each of one with a specific reactional medium. 

It should be economically viable. (This aspect has initiated a number of ongoing studies on the recycling and immobilization issues of lipase utilization for triglyceride hydrolysis.)14a,b... 

Saturated Fatty Acids in Position 2 of the Triglycerides. Hydrolysis with pancreatic lipase is followed by thin-layer chromatographic isolation of the monoglyceride fraction, which is converted to methyl esters. The methyl esters are analyzed... 

In the preparation of microemulsions and self-emulsifying systems, emulsions, or aqueous suspensions of medium-chain triglycerides, care should be taken to avoid microbiological contamination of the preparation, since lipase-producing microorganisms, which become active in the presence of moisture, can cause hydrolysis of the triglycerides. Hydrolysis of the triglycerides is revealed by the characteristic unpleasant odor of free medium-chain fatty acids. 

H. Mulder, L. S. Holst, H. Svensson, E. Degerman, F. Sundler, B. Ahren, P. Rorsman, and C. Holm, Hormone-sensitive lipase, the rate-limiting enzyme in triglyceride hydrolysis, is expressed and active in beta-cell, Diabetes, 1999, 48, 228-232. 

The products of triglyceride hydrolysis have only limited solubility in the aqueous environment of the intestinal lumen, as do other lipids which are present, such as cholesterol and fitt-soluble vitamins. For efficient lipid sol-... 

Figure 10 (Left) The rates of hydrolysis of emulsified long-chain triglycerides by pancreatic lipase. The highest rate occurs with triglycerides emulsified with gum arabic (no lecithin). All the other curves represent hydrolysis rates of triglycerides emulsified with long-chain lecithin. There is a long lag period and then a slight hydrolysis in the absence of additives. With added bile salts, the lag period is abolished, but the hydrolysis rates ate still low. Both colipase and colipase plus bile salts accelerate the hydrolytic rates. (Right) Concerted action of pancreatic lipase and phospholipase. Addition of phospholipase A2 hydrolyzes the phospholipid emulsifier (as indicated by the lysolecithin release), stops the lag phase, and initiates an accelerated triglyceride hydrolysis. (From Ref. 35.)...

Chylomicrons and remnants 1.006 Dietary triglycerides and cholesterol 10 1 B-48, E, A-L A-IV, C-L C-II, C-III Intestine Triglyceride hydrolysis by LPL ApoE-mediated remnant uptake by liver... 

Plasma VLDL is catabolized by LPL in the capillary beds in a process similar to the lipolytic processing of chylomicrons (Figure 35—1). When triglyceride hydrolysis is nearly complete, the VLDL remnants, usually termed intermediate-density lipoproteins (IDL), are released from the capillary endothelium and reenter the circulation. ApoB-100 containing small VLDL and IDL, which have a tj 2 minutes, have two potential fates 40-60% are cleared from the plasma... 

Orlistat inhibits pancreatic lipase and can block 30% of triglyceride hydrolysis in subjects eating a 30% fat diet. 

Taskinen, M.R., and Kuusi, T. (1987) Enzymes Involved in Triglyceride Hydrolysis, Baillieres Clin. Endocrinol. Metab. 7,639-666. 

The LDL may be considered as products of derivation from VLDL upon hydrolytic removal of a large portion of the glyceride moiety (Lindgren and Nichols, 1960). This appears to be supported by the demonstrated identity of their protein moiety (see Section II, C). One may be tempted to speculate that the state of aggregation of the LDL subunits in VLDL (see Section II, B) is maintained by the triglyceride moiety, so that they could be set free upon triglyceride hydrolysis. Testing of this hypothesis should be possible both in vitro and in vivo. 

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