Biology Reference
In-Depth Information
Chapter 8
The Chl
a
Carboxylic Biosynthetic Routes:
Protochlorophyllide
a
Great spirits have always encountered violent opposition from
mediocre minds (Albert Einstein).
8.1 Protochlorophyllide
a
(Pchlide
a
) Pool
Protochlorophyllide
a
(Pchlide
a
)(Fig.
8.1
) is the immediate precursor chlorophyllide
a
(Chlide
a
). The proposed role of Pchlide
a
as an intermediate in the Chl biosynthetic
pathway was based on the detection of Pchlide
a
in X-ray Chlorella mutants inhibited
in their capacity to form Chl (Granick
1950a
). It was conjectured that since the
mutants had lost the ability to form Chl but accumulated Pchlide
a
, the latter was a
logical precursor of Chl
a
. On the basis of absorbance spectroscopic determinations
the accumulated Mg-Proto was assigned by Granick a monovinyl (MV) chemical
structure (Fig.
8.1
, II), Pchlide with an ethyl group at positions 2 and a vinyl group at
position 4 of the tetrapyrrole macrocycle.
Granick proposed that Pchlide
a
was the immediate precursor of Pchlide
a
phytyl ester, a fully esterified Pchlide, which was wrongly believed at that time
to be the only precursor of Chl
a
in nature (Granick
1948
,
1950a
; Koski
1950
).
The biosynthetic function of Pchlide
a
as the precursor of chlorophyllide (Chlide)
a
,
one of the immediate precursors of Chl
a
, was not recognized till 7 years later
(Wolff and Price
1957
) when Pchlide
a
as a precursor of Chlide
a
was demonstrated
by conversion of Pchlide
a
to Chlide
a
.
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