The Chl a Carboxylic Biosynthetic Routes: Protochlorophyllide a - Chlorophyll Biosynthesis and Technological Applications - page 223

Biosynthesis of MV Pchlide a via Biosynthetic Route 0 in Etiolated DDV-LDV-
LDDV Plants in Darkness, and in Green DDV-LDV-LDDV Plants During
the Dark Phases of the Photoperiod
4VMpeR was detected in barley not in cucumber. Therefore this route should be
deleted if further research fails to detect 4VMpeR in DDV-LDV-LDDV plant
species.
Biosynthesis of MV Pchlide a via Biosynthetic Route 9 in Etiolated DDV-LDV-
LDDV Plants in Darkness, and in Green DDV-LDV-LDDV Plants During the Dark
Phases of the Photoperiod
Biosynthetic route 9 branches from route 8 and is proposed to account for the
formation of MV Pchlide b in green DDV-LDV-LDDV plant species in the light.
In this route MV Pchlide a is considered to be formed from DV Pchlide a by the
action of 4VPideR (Tripathy and Rebeiz 1988 ). It should be pointed out that even
during the light phases of the photoperiod DDV-LDV-LDDV plants form very small
amounts of MV Pchlide a in addition to the formation of massive amounts of DV
Pchlide a (Carey et al. 1985 ). It should also be stressed that in DDV-LDV-LDDV
plants, formation of MV Pchlide a via route 9 is destined exclusively for the
biosynthesis of MV Pchlide b in the light (Ioannides et al. 1997 ).
Biosynthetic Heterogeneity of MV Pchlide a via Routes 10, 11, 0 0 ,12in
DMV-LDV-LDMV Plant Species
In Fig. 8.8 , the biosynthesis of MV Pchlide a in DMV-LDV-LDMV plants is depicted
to occur in four different thylakoid environments as suggested by multiple resonance
energy transfer from MV Pchlide a to various Chl a -Protein complexes (Table 6.1 ,
Chap. 6 ) and (Kolossov et al. 2003 ), as well as further conversions to Chlides and Chls
as will be discussed later. It is unclear at this stage whether the spatial biosynthetic
heterogeneity of MV Pchlide a , is accompanied by chemical biosynthetic heterogene-
ity or not. In other words, it is unclear whether the proposed biosynthesis of MV
Pchlide a via routes 10, 11, 0 0 and 12 is catalyzed by identical Pchlide cyclases or by
different cyclase isozymes. These biosynthetic routes will be discussed further below.
Biosynthesis of MV Pchlide a in DMV-LDV-LDMV Plant Species via Routes 10
As depicted in Fig. 8.8 , MV Pchlide a in DMV-LDV-LDMV etiochloroplasts
in route 10 can be formed by reduction of the vinyl group of DV Pchlide a to
ethyl at position 4 of the macrocycle. The operation of route 10 in etiolated
DMV-LDV-LDMV plants is based on the fact that in isolated barley
etiochloroplasts DV Pchlide a is actively converted to MV Pchlide a by 4VPideR
(Tripathy and Rebeiz 1988 ).