Lipases, degradation

Nascent VLDLs are produced in the liver, and are composed predominantly of triacylglycerol. They contain a single molecule of apo B-100. Like nascent chylomicrons, VLDLs receive apo C-ll and apo E from HDLs in the plasma. VLDLs carry triacylglycerol from the liver to the peripheral tissues, where lipoprotein lipase degrades the lipid. 

A. HDL is produced in the liver. It transfers apoprotein Cn, which activates lipoprotein lipase, to chylomicrons and VLDL. HDL picks up cholesterol from cell membranes. This cholesterol is converted to cholesterol esters by the LCAT reaction. Ultimately, HDL enters liver cells by endocytosis and is digested by lysosomal enzymes. Hormone-sensitive lipase degrades triacylglycerols stored in adipose cells. 

Hoogewerf AJ, Cisar LA, Evans DC, Bensadoun A. Effect of chlorate on the sulfation of lipoprotein lipase and heparan sulfate proteoglycans. Sulfation of heparan sulfate proteoglycans affects lipoprotein lipase degradation. J Biol Chem 1991 266 16564-71. 

B. The liver and intestine are the main sonrces of circnlating lipids. Chylomicrons carry triacylglycerides and cholesterol esters from the intestine to other target tissues. VLDLs carry lipids from the liver into circulation. Lipoproteins are a mix of lipids and specific proteins and these complexes are classified based on their lipid/protein ratio. Lipoprotein lipases degrade the triacylglycerides in the chylomicrons and VLDLs with a concurrent release of apoproteins. This is a gradual process which converts the VLDLs into IDLs and then LDLs. 

The type of enzyme to be used, and quantification of degradation, will depend on the polymer being screened. For example, Mochizukiet studied the effects of draw ratio of polycaprolactone (PCL) fibres on enzymatic hydrolysis by lipase. Degradability of PCL fibres was monitored... 

Lipases degrade glycerides to glycerol and free fatty acids. Diacylglycerols in the free or phosphorylated form (phosphatidic acids) are precursors of groups of phospholipids that are important membrane constituents (Table 27). In the biosynthesis of these compounds the following reactions are of significance ... 

Dietary triacylglycerols are degraded to a small extent (via fatty acid release) by lipases in the low-pH environment of the stomach, but mostly pass untouched into the duodenum. Alkaline pancreatic juice secreted into the... 

Lipoproteins in Circulation Are Progressively Degraded by Lipoprotein Lipase... 

The enzymes used for modification of oils and fats are extraoelluar microbial lipases. They are excreted by micro-organisms into the growth medium to catalyse the degradation of lipids, and can be produced on a large scale by fermentation. 

A single hydrolase is usually inadequate for the degradation of a carrier, but most hydrolases have unspecific activities, i.e., they split the chains of polymers that are not their typical substrates. For example, chitosan is susceptible to lipases, pectinases, amylases among others [257-260]. 

Cutinase is a hydrolytic enzyme that degrades cutin, the cuticular polymer of higher plants [4], Unlike the oflier lipolytic enzymes, such lipases and esterases, cutinase does not require interfacial activation for substrate binding and activity. Cutinases have been largely exploited for esterification and transesterification in chemical synthesis [5] and have also been applied in laundry or dishwashing detergent [6]. 

The lipase-catalyzed fatty acid ester hydrolysis and the lipoxygenation of free polyunsaturated fatty acids are involved in the same lipid degradation pathway. They are respectively the first and second reaction in the lipoxygenase pathway (Fig. 3) [87-91]. The pathway produces volatile products of considerable importance in food technology including Cg[92, 93] or Cg- 94—96 aldehydes and alcohols from polyunsaturated fatty... 

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