Synopsis - Chlorophyll Biosynthesis and Technological Applications - page 48

reduction of the vinyl group to ethyl at position 4 of the macrocycle. In other words
he assumed that under normal etiolation or greening conditions, DV-Pchlide did
not accumulate, and was not detectable in green plants. By suspecting that the strange
Pchl fluorescence profile observed in plant extracts in ether at 77 K was due to
the presence of DV-Pchlide, we were proposing that contrary to previous assumptions
this Pchl did indeed accumulate ubiquitously in green plants.
To check the above hypothesis, we obtained samples of R spheroides
DV-Pchlide from June Lascelles who was then at UCLA, and recorded its fluores-
cence emission and excitation spectra in ether at 77 K. The recorded emission and
excitation peaks of standard DV Pchlide were identical to those observed in our
plant extracts (Belanger and Rebeiz 1979 ). In 1980, the chemical structure of the
newly detected DV Pchlide was ascertained by chemical derivatization (Belanger
and Rebeiz 1980c ) and in 1984, its chemical structure was confirmed by NMR
spectroscopy and mass spectroscopy (Wu and Rebeiz 1985 ). The metabolism of
MV and DV Pchlide a will be discussed in Chaps. 7 - 9 .
2.10.1.2 Discovery of Divinyl Chlorophyllide Occurrence in Green
Plants
To our surprise most of the accumulated DV Pchlide was found to be convertible
into Chl (Fig. 2.7 , 4d) (Belanger and Rebeiz 1979 ). Soon thereafter the accumulated
DV Pchlide was shown to be convertible into putative DV Chlide a (Fig. 2.7 , 4a)
(Belanger and Rebeiz 1980b ). The chemical structure of the newly formed DV
Chlide a was ascertained by chemical derivatization (Belanger et al. 1982 ) and in
1984, its chemical structure was confirmed by NMR and mass spectroscopy
(Wu and Rebeiz 1984 ). These observations, in addition to the suspected Chl
biosynthetic heterogeneity involved in the biosynthesis of Pchlide ester suggested
the existence of multiple biosynthetic routes during the biosynthesis of Chl. These
routes will be fully discussed in various chapters.
2.10.1.3 Discovery of the Occurrence of Divinyl
Protochlorophyllide Ester in Green Plants
In 1939 and 1940: Fischer and coworkers (Fischer and Oestricher 1940 ; Fishcher
et al. 1939 ) identified the protochlorophyll of pumpkin seed coat as a vinyl
pheoporphyrin analog of chlorophyll (Fig. 2.8 , II). Since this esterified MV Pchlide
differed from Chl by the absence of only two hydrogen atoms at the 7-8 position
of the tetrapyrrole macrocycle (Fig. 2.7 , 4d) they proposed that this esterified Pchl
was the immediate precursor of Chl. This notion was adopted by Granick and
became dogma until Wolfe and Price demonstrated that in green plants, the
immediate precursor of Chl was unesterified Chlide (Fig. 2.7 , 4a) (Wolff and
Price 1957 ). After 1957 Pchlide ester became a tetrapyrrole with an unknown
function and was no longer considered to be an intermediate in Chl biosynthesis.
Then in 1966, Jones reported that in addition to the esterified Pchl, i.e. MV Pchlide