Fatty acids location

Figure 24.8. Graphic presentation of the variation in specific optical rotation values for enantiopure MLM type asymmetrically structured TAG products 16a-16h, when varying the chain length of the saturated fatty acid located at the sn-3 position of the glycerol backbone.

A schematic representation of enzyme catalysed interesterification processes and products is shown in Figure 12.6. These processes generally involve hydrolysis and re-synthesis. Under restricted water conditions, interesterification is found to be predominant (Matsuo et aL, 1980, 1981 Coleman and Macrae, 1980). Chemically catalysed interesterification processes lead to randomization of the acyl groups along the glycerol chain. Using lipases with regio-specificity, the acyl transfers are restricted to the fatty acids located at the precise positions specific to the enzyme. 

A study involving two types of stmctured lipids (randomized v.s. specific product) revealed that the fatty acids located in the sn-2 position of TAG are preferentially absorbed (10). The randomized stmctured lipid used contained EPA, DHA and capric acid randomly distributed in the molecule. The specific stmctured lipid had EPA and DHA at the sn-2 position and capric acid at the sn-1 and snA positions of TAG. The concentrations of EPA and DHA in lyn5)hatics were higher in the specific stmctured lipid than in the randomized stmctured lipid. Rapid hydrolysis and absorption of stmctured lipids containing medium-chain fatty acids at the snA and snA positions and long-chain fatty acids at the sn-2 position have also been reported (II). 

Attacks triglycerides releasing fatty acids. Lipase A, hydrolyzes fatty acids located on the ends of triglycerides, whereas Upase A2has specificity for the middle fatty acid. Lipases are mainly produced in the aleurone layer. 

Specifically attacks phospholipids, Uberating fatty acids. Phospholipase A, hydrolyzes the fatty acid located on the end of the phospholipid, whereas phospholipase A2has specificity for the middle fatty acid. LysophosphoUpase frees the fatty acid from lysophosphoUpids or phospholipids initially hydrolyzed by phospholipase A,. 

Phosphorus. Eighty-five percent of the phosphoms, the second most abundant element in the human body, is located in bones and teeth (24,35). Whereas there is constant exchange of calcium and phosphoms between bones and blood, there is very Httle turnover in teeth (25). The Ca P ratio in bones is constant at about 2 1. Every tissue and cell contains phosphoms, generally as a salt or ester of mono-, di-, or tribasic phosphoric acid, as phosphoHpids, or as phosphorylated sugars (24). Phosphoms is involved in a large number and wide variety of metaboHc functions. Examples are carbohydrate metaboHsm (36,37), adenosine triphosphate (ATP) from fatty acid metaboHsm (38), and oxidative phosphorylation (36,39). Common food sources rich in phosphoms are Hsted in Table 5 (see also Phosphorus compounds). 

These oxazolines have cationic surface-active properties and are emulsifying agents of the water-in-oil type. They ate acid acceptors and, in some cases, corrosion inhibitors (see Corrosion). Reaction to oxazoline also is useful as a tool for determination of double-bond location in fatty acids (2), or for use as a protective group in synthesis (3). The oxazolines from AEPD and TRIS AMINO contain hydroxyl groups that can be esterified easily, giving waxes (qv) with saturated acids and drying oils (qv) with unsaturated acids. 

The space inside the inner mitochondrial membrane is called the matrix, and it contains most of the enzymes of the TCA cycle and fatty acid oxidation. (An important exception, succinate dehydrogenase of the TCA cycle, is located in the inner membrane itself.) In addition, mitochondria contain circular DNA molecules, along with ribosomes and the enzymes required to synthesize proteins coded within the mitochondrial genome. Although some of the mitochondrial proteins are made this way, most are encoded by nuclear DNA and synthesized by cytosolic ribosomes. 

All of the other enzymes of the /3-oxidation pathway are located in the mitochondrial matrix. Short-chain fatty acids, as already mentioned, are transported into the matrix as free acids and form the acyl-CoA derivatives there. However, long-chain fatty acyl-CoA derivatives cannot be transported into the matrix directly. These long-chain derivatives must first be converted to acylearnitine derivatives, as shown in Figure 24.9. Carnitine acyltransferase I, located on the outer side of the inner mitochondrial membrane, catalyzes the formation of... 

Figure 27.1 A soap micelle solubilizing a grease particle in water. An electrostatic potential map of a fatty acid carboxylate shows how the negative charge is located in the head group.

The steps in the subsequent utilization of muscle LCFAs may be summarized as follows. The free fatty acids, liberated from triglycerides by a neutral triglyceride lipase, are activated to form acyl CoAs by the mediation of LCFAcyl-CoA synthetase which is situated on the outer mitochondrial membrane. The next step involves carnitine palmitoyl transferase I (CPT I, see Figure 9) which is also located on the outer mitochondrial membrane and catalyzes the transfer of LCFAcyl residues from CoA to carnitine (y-trimethyl-amino-P-hydroxybutyrate). LCFAcyl... 

The intracellular and plasma membranes have a complex structure. The main components of a membrane are lipids (or phospholipids) and different proteins. Lipids are fatlike substances representing the esters of one di- or trivalent alcohol and two aliphatic fatty acid molecules (with 14 to 24 carbon atoms). In phospholipids, phosphoric acid residues, -0-P0(0 )-O-, are located close to the ester links, -C0-0-. The lipid or phospholipid molecules have the form of a compact polar head (the ester and phosphate groups) and two parallel, long nonpolar tails (the hydrocarbon chains of the fatty acids). The polar head is hydrophihc and readily interacts with water the hydrocarbon tails to the... 

Hydrolysis of triacylglycerides in tissues is effected by a tissue enzyme, tri-acylglyceride lipase, which hydrolyzes triacylglycerides to glycerol and free fatty acids. There are a variety of tissue lipases that differ primarily in their optimum pH and their location in the cell. The acidic lipase is contained in lysosomes the basic lipase, in microsomes and the neutral lipase, in cytoplasm. A specific feature of the tissue lipase is its sensitivity to hormones which, by activating adenylate cyclase, elicit the transition of the inactive tissue lipase to its active... 

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