3 Phycobiliproteins in Microalgae: Occurrence …
53
are found in homodimers, heterodimers, and tetramers and remain in bind state with
fatty acids, vitamins, and carotenoids ligands (Grzyb et al. 2006). Another type of
bilin lyase is named as Cpc T which is expressed by cpcT gene and cpeCDESTR
gene cluster in Fremyella diplosiphon (Cobley et al. 2002). Certain cryptophytic
Guillardia theta also encodes Cpc T lyase enzymes (Bolte et al. 2008). In addition,
certain cyanophage such as Prochlorococcus P-HM1 also contains cpeT which
play an important role in the functional integration of open chain chromophores to
Cys-155 of β-subunits (Gasper et al. 2017). Recently, the crystal structure of CpcT
(T-type lyase) has been demonstrated in the cyanobacterium Nostoc (Anabaena) sp.
PCC 7120 (Zhou et al. 2014). The Y/Z-type lyases are playing an important role in the
functionality of PE-I and PE-II. Lyases are heterodimer and catalyze chromophore
binding in α- and β-subunits of PE (Scheer and Zhao 2008). Recently, an isomerase
enzyme (Mpe Z) has been reported in the cyanobacterium Synechococcus sp. which
catalyzed chromophore interaction in α-subunit of PEII and also involves in the
conversion of PEB to PUB (Shukla et al. 2012) (Table 3.2).
3.6 Stress Adaptability and Commercial Productivity
In the current scenario, production of value-added compounds from microalgae is of
great interest for industries. Among value-added compounds, most of the industry
focuses on production of PBPs in large scale. However, the rate of production is
severally affected in various abiotic stress conditions. Thus there is an utmost need
to acclimatize and optimize cyanobacteria for large scale production of PBPs from
most of the cyanobacteria. In this section, we have elaborated the effects of stress on
cyanobacteria related to production and adaptation of methodology for commercial
production of PBPs.
3.6.1 Light
Nitrogen-fixing cyanobacteria have an obligatory mechanism of photosynthesis in
the presence of solar spectrum. In PBPs subunits, PC absorbs in the yellow–red
regions, whereas PE absorbs in the green range of solar spectrum. The environmental adaptability of cyanobacteria under various light regimes is not uniformly
constant and it varies among the cyanobacteria. It has been reported that ultraviolet radiation exhibits several effects on the structure and productivity of PBPs. UV
radiation has high intensity of energy that is able to produce different types of reactive oxygen species (ROS) inside the cell which indirectly cause several damages
in biomolecules such as proteins, lipids, and nucleic acids (Gao et al. 2007, Singh
et al. 2014, Kannaujiya et al. 2014). Tyagi et al. (1992) PE-rich strain of Nostoc
sp. was found to be more tolerant under UV-B irradiation as compared to PC-rich
cyanobacteria. UV radiations also affect the composition of linker polypeptides
53
are found in homodimers, heterodimers, and tetramers and remain in bind state with
fatty acids, vitamins, and carotenoids ligands (Grzyb et al. 2006). Another type of
bilin lyase is named as Cpc T which is expressed by cpcT gene and cpeCDESTR
gene cluster in Fremyella diplosiphon (Cobley et al. 2002). Certain cryptophytic
Guillardia theta also encodes Cpc T lyase enzymes (Bolte et al. 2008). In addition,
certain cyanophage such as Prochlorococcus P-HM1 also contains cpeT which
play an important role in the functional integration of open chain chromophores to
Cys-155 of β-subunits (Gasper et al. 2017). Recently, the crystal structure of CpcT
(T-type lyase) has been demonstrated in the cyanobacterium Nostoc (Anabaena) sp.
PCC 7120 (Zhou et al. 2014). The Y/Z-type lyases are playing an important role in the
functionality of PE-I and PE-II. Lyases are heterodimer and catalyze chromophore
binding in α- and β-subunits of PE (Scheer and Zhao 2008). Recently, an isomerase
enzyme (Mpe Z) has been reported in the cyanobacterium Synechococcus sp. which
catalyzed chromophore interaction in α-subunit of PEII and also involves in the
conversion of PEB to PUB (Shukla et al. 2012) (Table 3.2).
3.6 Stress Adaptability and Commercial Productivity
In the current scenario, production of value-added compounds from microalgae is of
great interest for industries. Among value-added compounds, most of the industry
focuses on production of PBPs in large scale. However, the rate of production is
severally affected in various abiotic stress conditions. Thus there is an utmost need
to acclimatize and optimize cyanobacteria for large scale production of PBPs from
most of the cyanobacteria. In this section, we have elaborated the effects of stress on
cyanobacteria related to production and adaptation of methodology for commercial
production of PBPs.
3.6.1 Light
Nitrogen-fixing cyanobacteria have an obligatory mechanism of photosynthesis in
the presence of solar spectrum. In PBPs subunits, PC absorbs in the yellow–red
regions, whereas PE absorbs in the green range of solar spectrum. The environmental adaptability of cyanobacteria under various light regimes is not uniformly
constant and it varies among the cyanobacteria. It has been reported that ultraviolet radiation exhibits several effects on the structure and productivity of PBPs. UV
radiation has high intensity of energy that is able to produce different types of reactive oxygen species (ROS) inside the cell which indirectly cause several damages
in biomolecules such as proteins, lipids, and nucleic acids (Gao et al. 2007, Singh
et al. 2014, Kannaujiya et al. 2014). Tyagi et al. (1992) PE-rich strain of Nostoc
sp. was found to be more tolerant under UV-B irradiation as compared to PC-rich
cyanobacteria. UV radiations also affect the composition of linker polypeptides