The Chl a Carboxylic Biosynthetic Routes: Conversion of Chlide a to Chl a - Chlorophyll Biosynthesis and Technological Applications - page 258

catalyzed by PORB as discussed in Sect. IIIB of Chap. 9 . Based on the prevalence
of direct phytylation of MV Chlide a in green(ing) tissues (Soll and Schultz 1981 ),
it is our guess that most of the conversion of nascent MV Chlide a to MV Chl a in
route 10, proceeds by direct esterification of MV Chlide a with phytol. Since most
of the Chl a is formed in the light, the size of the MV Chl a pool formed via route
7 is most probably very substantial.
Moreover, since under continuous illumination, most of the synthesized Chl
consists of MV Chl a , and b located in antenna Chl-protein complexes,
(Akoyunoglou et al. 1981 ; Alberte et al. 1972 ), we propose that the MV Chl
a formed via route 10 is destined to LHCII and other antenna Chl-protein complexes.

10.1.4.2 Biosynthesis of MV Chlorophyll via Route 0 0 in Greening

DMV-LDV-LDMV Plants During the Light Phases
of the Photoperiod

a

In biosynthetic route 10, DV Mpe is converted to MV Mpe by 4VMpeR (Kolossov
and Rebeiz 2001 ). Then MV Mpe is converted to MV Chlide a probably via
POR-B and the latter to Chl a probably by direct phytylation (Daniell and Rebeiz
1984 ; Soll and Schultz 1981 ).

10.1.4.3 Biosynthesis of MV Chlorophyll via Route 12 in Etiolated

DMV-LDV-LDMV Plants After Exposure to Light,
and in Greening DMV-LDV-LDMV Plants During
the Initial Dark Phases of the Photoperiod

a

Etiolated DMV-LDV-LDMV plants accumulate mostly MV Pchlide a . Upon
exposure to light, MV Pchlide a is converted to MV Chlide a by PORA as described
in section IIIB of Chap. 9 . Since in etiolated tissues, MV Chlide a conversion to MV
Chl a takes place via esterification with GG (Schoch 1978 ), it is our guess that,
conversion of the nascent MV Chlide a to MV Chl a via route 12 takes place via Chl
a -GG followed by stepwise hydrogenation to Chl a -Phytol as described in Sect. 1.1 .
This route is also most probably functional in DMV-LDV-LDMV plants growing
under photoperiodic conditions, at the onset of illumination, during the first few
dark cycles of the photoperiod when t-LW-Pchlide a accumulation is substantial
(Cohen et al. 1977 ; Cohen and Rebeiz 1978 ).
Since during the initial phases of greening of etiolated tissues, most of the
Chl consists of MV Chl a , located in PSI and PSII (Akoyunoglou et al. 1981 ;
Alberte et al. 1972 ), we propose that the MV Chl a formed via route 12 is destined
to PSI and/or PSII Chl-protein complexes.