Food Lipids: Chemistry, Nutrition, and Biotechnology

L.) leaf peroxisomes exhibits higher activity toward long chain fatty acids [21,22]
and low activity toward short chain acyl CoAs. The acyl-CoA oxidase of mung bean
hypocotyl peroxisomes, which in other respects exhibits kinetic properties similar to
those outlined above for the enzymes from other sources, shows an additional, pronounced
optimum of activity with butyryl CoA as substrate [21–23]. Activity with
butyryl CoA considerably higher than that obtained with palmitoyl CoA has also
been reported for the acyl-CoA oxidase of peroxisomes from tubers of Jerusalem
artichoke (Helianthus tuberosus L.) and pea (Pisum sativum L.) cotyledons [13,24].
The acyl-CoA oxidases of peroxisomes from the scutella of rape cotyledons and
maize (Zea mays L.) shows a very strong preference for C 12 and/or C 14 acyl-CoA
with respect to activity [16]. Thus substrate specificity of acyl-CoA oxidases appears
to depend on the enzyme sources.
The reactions leading from 2E-enoyl-CoA to L-3-hydroxyacyl-CoA and from
L-3-hydroxyacyl-CoA to 3-oxo-acyl-CoA are catalyzed by one and the same protein
[25], which exhibits both enoyl-CoA hydratase (EC 4.2.1.17) and L-3-hydroxyacyl-
CoA dehydrogenase (EC 1.1.1.35) activity in plant peroxisomes. Behrends et al. [26],
who studied glyoxysomes from cucumber cotyledons and peroxisomes from green
leaves of Lens culinaris L., found two isoforms of the multifunctional protein (M r
74 and 76.5 kDa) and showed that these differ both in molecular structure and in
kinetic properties. The ratio of 2-enoyl-CoA hydratase activity to L-3-hydroxyacyl-
CoA dehydrogenase activity for the 76.5-kDa protein is three times higher (approximately
10.0) than for the 74-kDa protein. The 2-enoyl-CoA hydratase activity of
glyoxysomes from cotton (Gossypium hirsutum L.) cotyledons decreases (100-fold)
with increasing chain length of the enoyl-CoA (C 4 to C 16) [27]. The K m value for the
enyol CoAs of chain length C 4 to C 16 increased approximately 10-fold over the chain
length range studied.
So far, there are no reports concerning kinetic properties of the 3-oxo-acyl-
CoA thiolase (EC 2.3.1.16) of plant peroxisomes.
Although peroxisomal �-oxidation described above is based predominantly on
the type of individual enzymatic reaction involved in �-oxidation instead of identification
of the intermediates themselves or the products of the individual enzymatic
reactions, the complete degradation of fatty acids by plant peroxisomes was demonstrated
by Donaldson and Fang [28] using 16:0 substrate (concentrations