Biology Reference
In-Depth Information
Chemical Heterogeneity of the Long Chain Fatty Alcohols at Position
7 of the Pchlide
a
E Macrocycle
As early as 1958 various researchers started questioning the assumed phytol
nature of the long chain fatty alcohol that esterified the propionic acid residue at
position 7 of the Pchlide
a
ester macrocycle (Rebeiz and Castelfranco
1973
).
For example gas chromatographic analysis of the hydrolyzed fatty alcohol frac-
tion of Pchlide
a
ester of etiolated cucumber cotyledons failed to detect any phytol
(McCarthy et al.
1981
; Rebeiz and Castelfranco
1973
). On the other hand, the
Pchlide
a
ester of etiolated barley leaves was shown to contain geranylgeraniol
(GG) instead of phytol (Liljenberg
1974
). The inner seed coat of Cucurbitaceae, a
rich source of Pchlide
a
ester was shown to contain a large number of Pchlide
a
esters esterified with different long chain alcohols. The latter consisted of
farnesol and all possible C20 alcohols including GG and phytol (Shioi and
Sasa
1982
). Roots of etiolated wheat, accumulated large amounts of MV
Pchlide
a
esters and lesser amounts of MV Pchlide
a
. The alcohol moieties of
the four accumulated Pchlide
a
esters consisted of GG, dihydrogeranyl-
graniol (GHGG), tetrahydrogeranylgraniol (THGG) and phytol (Mc Ewen and
Lindsten
1992
).
Monovinyl (MV) and Divinyl (DV) Chemical Heterogeneity at Position
4 of the Pchlide
a
E Macrocycle
The Occurrence of DV Pchlide
a
ester in higher plants was first reported in the inner
seed coat of
Cucurbita pepo
(pumpkin) (Jones
1966
), and was confirmed by
(Houssier and Sauer
1969
) (Fig.
11.6
). The search for the occurrence of DV Pchlide
a
ester in other higher plant tissues was however unsuccessful till 11 years later
(Belanger and Rebeiz
1980a
,
b
). Using sensitive spectrofluorometric techniques, it
was possible to show that etiolated cucumber cotyledons, a DDV-LDV-LDDV plant
species incubated in darkness with ALA, accumulated mainly MV Pchlide a E and
detectable, yet small amounts of DV Pchlide
a
E. The two Pchlide
a
E were
separated by chromatography on thin layers of polyethylene and were characterized
by fluorescence emission and excitation spectra at room temperature and 77
K.
However, these studies were not extended with rigor to other plant species such as
wheat, corn and barley. In other words, it is not certain at this stage whether small
amounts of DV Pchlide
a
E also occur in DMV-LMV-LDMV plant species such as
johnsongrass and DMV-LDV-LDMV plant species such as barley, wheat and corn.
Biosynthetic Heterogeneity of Pchlide
a
E
Because of (a) the DV-MV nature of the Mpde and Pchlide
a
E pools, and
(b) because of the structural similarities between Mpde and Pchlide
a
E, one fully
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