4 Carotenoid Synthesis and Accumulation in Microalgae …
71
2011). X-ray structural analyses indicated that the monomer of peripheral LHC of
PSII (LHC-II) of land plants has four carotenoid-binding sites for two luteins, one
neoxanthin, and one violaxanthin or zeaxanthin (Liu et al. 2004; Standfuss et al.
2005). Carotenoids in peripheral LHCII can transfer their excitation energy to their
nearest/neighbor chlorophylls.
Bacillariophyceae and diatoms possess fucoxanthin-chlorophyll a/c binding
proteins (FCP). FCP associates with core complex of PSI and PSII, and functions as
the peripheral antenna in the light harvesting and in energy transfer (Nagao et al. 2007;
Ikeda et al. 2008; Nagao et al. 2014). Dinoflagellate employs peridinin-chlorophyllprotein (PCP), a unique water-soluble protein located in the thylakoid lumen, for
the light harvesting, in addition to the LHC in the thylakoid membrane (Polívka
et al. 2007). The PCP complex of a dinoflagellate Amphidinium carterae consists
of trimeric subunits with two pseudo-identical domains containing densely packed
peridinin and chlorophyll a in a stoichiometric ratio of 4:1 (Hofmann et al. 1996).
4.3 Photoprotection by Carotenoids
In the photochemical reaction of photosynthesis, excess light energy can generate
various reactive oxygen species (ROS), such as superoxide radical (O 2
− ), hydrogen
peroxide (H 2 O 2 ), hydroxyl radical (•OH), and singlet oxygen (
1 O 2 ) (Edreva 2005,
Krieger-Liszkay 2005; Asada 2006; Telfer 2014). ROS can cause the cleavage of
D1 protein in PSII and can inhibit the repair of photodamaged PSII resulting in the
photoinhibition of photosynthesis (Mishra and Ghanotakis 1994; Miyao et al. 1995;
Okada et al. 1996; Nishiyama et al. 2004).
Xanthophylls in peripheral LHCII (mainly lutein in the L1 and L2 sites of LHCII) can quench triplet-state chlorophylls in close van der Waals contact to prevent
the formation of singlet oxygen (Standfuss et al. 2005; Triantaphylidès and Havaux
2009). In addition, violaxanthin and zeaxanthin in a pocket at the monomer interface of LHC-II participate in the regulation of inducible energy-dependent nonphotochemical quenching (qE) via deepoxidation/epoxidation of xanthophylls called
a xanthophyll cycle (violaxanthin cycle) (Müller et al. 2001; Liu et al. 2004; Standfuss
et al. 2005). Several algae such as Haptophyta, Dinoflagellate, and diatoms employ
another type of xanthophyll cycle called diadinoxanthin cycle, which consists of
a conversion of diadinoxanthin to diatoxanthin, for the non-photochemical energy
dissipation (Goss and Jakob 2010).
In the PCP complex of dinoflagellate, peridinin can quench triplet-state chlorophyll a (Bautista et al. 1999; Alexandre et al. 2007; Schulte et al. 2009). Cyanobacteria
utilize the orange carotenoid protein (OCP), a water-soluble photosensory protein, for
the photoprotection. OCP contains 3
-hydroxyechinenone as the photoactive chromophore and triggers light-induced non-photochemical quenching by interacting
with light-harvesting phycobilisomes under blue-green light (Kerfeld et al. 2003;
Wilson et al. 2006, 2008; Harris et al. 2016). OCP can also function as a singlet
oxygen quencher in cyanobacteria (Sedoud et al. 2014).
71
2011). X-ray structural analyses indicated that the monomer of peripheral LHC of
PSII (LHC-II) of land plants has four carotenoid-binding sites for two luteins, one
neoxanthin, and one violaxanthin or zeaxanthin (Liu et al. 2004; Standfuss et al.
2005). Carotenoids in peripheral LHCII can transfer their excitation energy to their
nearest/neighbor chlorophylls.
Bacillariophyceae and diatoms possess fucoxanthin-chlorophyll a/c binding
proteins (FCP). FCP associates with core complex of PSI and PSII, and functions as
the peripheral antenna in the light harvesting and in energy transfer (Nagao et al. 2007;
Ikeda et al. 2008; Nagao et al. 2014). Dinoflagellate employs peridinin-chlorophyllprotein (PCP), a unique water-soluble protein located in the thylakoid lumen, for
the light harvesting, in addition to the LHC in the thylakoid membrane (Polívka
et al. 2007). The PCP complex of a dinoflagellate Amphidinium carterae consists
of trimeric subunits with two pseudo-identical domains containing densely packed
peridinin and chlorophyll a in a stoichiometric ratio of 4:1 (Hofmann et al. 1996).
4.3 Photoprotection by Carotenoids
In the photochemical reaction of photosynthesis, excess light energy can generate
various reactive oxygen species (ROS), such as superoxide radical (O 2
− ), hydrogen
peroxide (H 2 O 2 ), hydroxyl radical (•OH), and singlet oxygen (
1 O 2 ) (Edreva 2005,
Krieger-Liszkay 2005; Asada 2006; Telfer 2014). ROS can cause the cleavage of
D1 protein in PSII and can inhibit the repair of photodamaged PSII resulting in the
photoinhibition of photosynthesis (Mishra and Ghanotakis 1994; Miyao et al. 1995;
Okada et al. 1996; Nishiyama et al. 2004).
Xanthophylls in peripheral LHCII (mainly lutein in the L1 and L2 sites of LHCII) can quench triplet-state chlorophylls in close van der Waals contact to prevent
the formation of singlet oxygen (Standfuss et al. 2005; Triantaphylidès and Havaux
2009). In addition, violaxanthin and zeaxanthin in a pocket at the monomer interface of LHC-II participate in the regulation of inducible energy-dependent nonphotochemical quenching (qE) via deepoxidation/epoxidation of xanthophylls called
a xanthophyll cycle (violaxanthin cycle) (Müller et al. 2001; Liu et al. 2004; Standfuss
et al. 2005). Several algae such as Haptophyta, Dinoflagellate, and diatoms employ
another type of xanthophyll cycle called diadinoxanthin cycle, which consists of
a conversion of diadinoxanthin to diatoxanthin, for the non-photochemical energy
dissipation (Goss and Jakob 2010).
In the PCP complex of dinoflagellate, peridinin can quench triplet-state chlorophyll a (Bautista et al. 1999; Alexandre et al. 2007; Schulte et al. 2009). Cyanobacteria
utilize the orange carotenoid protein (OCP), a water-soluble photosensory protein, for
the photoprotection. OCP contains 3
-hydroxyechinenone as the photoactive chromophore and triggers light-induced non-photochemical quenching by interacting
with light-harvesting phycobilisomes under blue-green light (Kerfeld et al. 2003;
Wilson et al. 2006, 2008; Harris et al. 2016). OCP can also function as a singlet
oxygen quencher in cyanobacteria (Sedoud et al. 2014).