15 Application of Lipoxygenases and Related
Enzymes for the Preparation of Oxygenated
Lipids
Ivo Feussner and Hartmut Ku ̈hn
15.1 Introduction
Lipoxygenases (linoleate: oxygen oxidoreductases; EC 1.13.11.12; LOXs) constitute
a family of lipid-peroxidizing enzymes which are widely distributed in the plant and
animal kingdom (Brash, 1999). They contain one nonheme iron per mole enzyme
and catalyze the regio- and stereoselective dioxygenation of polyenoic fatty acids
forming S-configurated hydroperoxy derivatives (Rosahl, 1996). In mammals,
LOXs are classified into 5-, 8-, 12-, and 15-LOXs according to their positional spe-
cificity of arachidonic acid (AA) oxygenation (Yamamoto, 1992). This classification
is straightforward and commonly used, but suffers from several disadvantages which
may lead to confusions among scientists not working in the field. Since AA is either
not present in higher plants or is a minor constituent of storage lipids, plant LOXs are
classified into 9- and 13-LOXs with respect to their positional specificity of linoleic
acid (LA) oxygenation (Gardner, 1991). For many years plant and animal LOXs have
been considered to oxygenate mainly free polyenoic fatty acids forming oxygenated
derivatives which may exhibit biological activities (Ford-Hutchinson et al., 1994;
Ku ̈hn, 1996; Rosahl, 1996). However, more recent studies suggested that certain
plant and animal LOX-isoforms are capable of oxygenating also ester lipid sub-
strates, such as phospholipids (Brash et al., 1987; Murray and Brash, 1988), triacyl-
glycerols (Feussner et al., 1995; 1998) and cholesterol esters (Belkner et al., 1991).
Even more complex lipid–protein assemblies such as biomembranes (Ku ̈hn et al.,
1990a; Maccarrone et al., 1994) and lipoproteins (Belkner et al., 1993; Upston et al.,
1996) were metabolized by LOXs.
Oxygenation of naturally occurring polyunsaturated fatty acids may proceed en-
zymatically and nonenzymatically. Both reactions lead to the formation of hydro-
peroxy fatty acids, but there are important differences between the two processes
(Ku ̈hn and Thiele, 1999). The most important difference is the specificity of the
product pattern. Nonenzymatic lipid peroxidation leads to an unspecific product
mixture consisting of various positional and optical isomers. These product isomers
can be separated by a combination of reverse-phase, straight-phase and chiral-phase
high performance liquid chromatography (HPLC). These separation procedures are
rather laborious and require special equipment such as HPLC devices and suitable
columns. In contrast, during LOX reaction polyenoic fatty acids are usually oxyge-
nated to one specific product isomer which exhibits a high degree of optical purity.
Thus, for large-scale preparation of structurally well-defined oxygenated polyenoic
fatty acids, LOX isoenzymes exhibiting different positional specificities may be
used. However, for the time being it is not possible to prepare all hydro(pero)xy
Enzymesin LipidModification.Editedby UweT. Bornscheuer
Copyright 2000 Wiley-VCHVerlagGmbH& Co. KGaA,Weinheim.ISBN:3-527-30176-3
