Fatty acid terms Links

The amino group of sphingosine is acylated with long-chain fatty acids and the N-acylated product is termed a ceramide (Fig. 3-3). C-l of ceramide is linked to different... 

The degradation of the fatty acids occurs in the mitochondrial matrix through an oxidative cycle in which C2 units are successively cleaved off as acetyl CoA activated acetic acid). Before the release of the acetyl groups, each CH2 group at C-3 of the acyl residue (the P-C atom) is oxidized to the keto group— hence the term p-oxidation for this metabolic pathway. Both spatially and functionally, it is closely linked to the tricarboxylic acid cycle (see p. 136) and to the respiratory chain (see p. 140). 

The polyketides are a large family of bio synthetically related NPs, some of which have very great pharmaceutical value (polyketide sales total about 10 billion annually, see also Chapter 7). Some antibiotics (erythromycin, monensin, rifamycin), immunosuppressants (rapamycin), antifungal substances (amphotericin), antiparasitic (aver-mectin) and anticancer drugs (doxorubicin) are polyketides. The term polyketide refers to the fact that the basic carbon skeleton is not a simple hydrocarbon chain as in the case of fatty acids but is a series of linked keto groups in sequence (Figure 3.6). The first phase of this pathway, the generation of carbon skeleton diversification. 

Oxidative cleavage at double bonds, the process of rancidification, is undesirable in foods because of the bad taste of the oxidation products. Oxidation can also lead to polymerization or cross-linking of fatty acid chains. This exothermic process is useful in terms of setting a finish on paints and dangerous if it occurs with combustible materials in an enclosed space. 

Although the term lipoprotein can describe any protein that is covalently linked to lipid groups (e.g., fatty acids or prenyl groups), it is most often used for a group of molecular complexes found in the blood plasma of mammals (especially humans). Plasma lipoproteins transport lipid molecules (triacylglycerols, phospholipids, and cholesterol) through the bloodstream from one organ to another. Lipoproteins also contain several types of lipid-soluble antioxidant molecules (e.g., a-tocopherol and several carotenoids). (The function of antioxidants, substances that protect biomolecules from free radicals, is described in Chapter 10.) The protein components of lipoproteins are called apolipoproteins or apoproteins. 

The terms NEFA, unesterified fatty acids, and free fatty acids have been used synonymously in the literature, although these fatty acids are mainly bound to plasma proteins. Enzymatic assays are convenient with NEFA in the presence of added acyl-coenzyme A (CoA) synthetase forming acyl CoA esters, which are then oxidized by acyl CoA oxidase to yield hydrogen peroxide. The hydrogen peroxide produced is measured by a peroxidase-linked colorimetric detection reaction. Plasma samples should be separated promptly and stored frozen to prevent in vitro lipolysis (Zambon, Hashimoto, and Brunzell 1993). 

Tristearin is simply the chemical term for a type of fat. Fats are composed of fatty acids joined to a molecule of glycerol, so they are also called triglycerides. Tristearin, a fat found in tallow, is made of three molecules of stearic acid linked to a glycerol molecule. When it is chemically reacted with a base — like sodium carbonate, which is found in ashes — it forms sodium stearate, otherwise known as soap. 

---