28
S. Takaichi
Table 2.2 (continued)
Gene
Enzyme
Species
References
crtO
β-Carotene ketolase
Anabaena sp. PCC
7120
Gloeobacter violaceus
PCC 7421
Synechocystis sp. PCC
6803
Mochimaru et al. (2005)
Steiger et al. (2005)
Makino et al. (2008)
Lagarde et al. (2000)
Fernández-González
et al. (1997)
crtW, bkt
β-Carotene ketolase
Anabaena sp. PCC
7120
Gloeobacter violaceus
PCC 7421
Nostoc punctiforme
PCC 73102
Chlorella zofingiensis
ATCC 30412
Haematococcus
pluvialis NIES-144
Haematococcus
pluvialis strain 34/7
Makino et al. (2008),
Mochimaru et al. (2005)
Steiger et al. (2005)
Tsuchiya et al. (2005)
Steiger and Sandmann
(2004)
Huang et al. (2006a)
Kajiwara et al. (1995)
Huang et al. (2006b)
Lotan and Hirschberg
(1995)
to yield geranylgeranyl pyrophosphate (C 20 ). In a condensation of the two C 20
compounds, the first carotene, phytoene (C 40 ), is formed by phytoene synthase (CrtB,
Pys, Psy) using ATP (Sandmann 1994, Armstrong 1997). This pathway has been
confirmed by cloning genes from two species of Rhodobacter (purple bacteria)
and two species of Pantoea (Misawa et al. 1990; Sandmann 1994; Armstrong
1997). Among oxygenic phototrophs, the functions of CrtE and CrtB have also
been confirmed (Table 2.2). The crtE and crtB genes exhibit high DNA sequence
similarity from bacteria to land plants, respectively (Takaichi 2011).
2.3.1.2 Phytoene to Lycopene Synthesis
Four desaturation steps are needed in the conversion of phytoene to lycopene.
Oxygenic phototrophs require four enzymes: phytoene desaturase (CrtP, Pds), ζcarotene desaturase (CrtQ, Zds), ζ-carotene isomerase (Z-ISO), and cis-carotene
isomerase (CrtH, CrtISO) (Fig. 2.2). CrtP catalyzes the first two desaturation steps
from phytoene to ζ-carotene via phytofluene, and CrtQ catalyzes two additional
desaturation steps from ζ-carotene to lycopene via neurosporene. During desaturation by CrtP, 9,15,9
-tri-cis ζ-carotene is produced, and this is converted to 9,9
-dicis ζ-carotene, as in Arabidopsis by Z-ISO. Light is also effective for this reaction
(Sugiyama et al. 2020). During desaturation by CrtQ, neurosporene and lycopene are
isomerized to poly-cis forms, and then CrtH isomerizes to all-trans forms. Light is
also effective for their photoisomerization to all-trans forms (Masamoto et al. 2001).
The functions of these enzymes have mainly been confirmed in cyanobacteria, green
algae and land plants (Table 2.2), CrtP and Z-ISO from Arthrospira platensis and
S. Takaichi
Table 2.2 (continued)
Gene
Enzyme
Species
References
crtO
β-Carotene ketolase
Anabaena sp. PCC
7120
Gloeobacter violaceus
PCC 7421
Synechocystis sp. PCC
6803
Mochimaru et al. (2005)
Steiger et al. (2005)
Makino et al. (2008)
Lagarde et al. (2000)
Fernández-González
et al. (1997)
crtW, bkt
β-Carotene ketolase
Anabaena sp. PCC
7120
Gloeobacter violaceus
PCC 7421
Nostoc punctiforme
PCC 73102
Chlorella zofingiensis
ATCC 30412
Haematococcus
pluvialis NIES-144
Haematococcus
pluvialis strain 34/7
Makino et al. (2008),
Mochimaru et al. (2005)
Steiger et al. (2005)
Tsuchiya et al. (2005)
Steiger and Sandmann
(2004)
Huang et al. (2006a)
Kajiwara et al. (1995)
Huang et al. (2006b)
Lotan and Hirschberg
(1995)
to yield geranylgeranyl pyrophosphate (C 20 ). In a condensation of the two C 20
compounds, the first carotene, phytoene (C 40 ), is formed by phytoene synthase (CrtB,
Pys, Psy) using ATP (Sandmann 1994, Armstrong 1997). This pathway has been
confirmed by cloning genes from two species of Rhodobacter (purple bacteria)
and two species of Pantoea (Misawa et al. 1990; Sandmann 1994; Armstrong
1997). Among oxygenic phototrophs, the functions of CrtE and CrtB have also
been confirmed (Table 2.2). The crtE and crtB genes exhibit high DNA sequence
similarity from bacteria to land plants, respectively (Takaichi 2011).
2.3.1.2 Phytoene to Lycopene Synthesis
Four desaturation steps are needed in the conversion of phytoene to lycopene.
Oxygenic phototrophs require four enzymes: phytoene desaturase (CrtP, Pds), ζcarotene desaturase (CrtQ, Zds), ζ-carotene isomerase (Z-ISO), and cis-carotene
isomerase (CrtH, CrtISO) (Fig. 2.2). CrtP catalyzes the first two desaturation steps
from phytoene to ζ-carotene via phytofluene, and CrtQ catalyzes two additional
desaturation steps from ζ-carotene to lycopene via neurosporene. During desaturation by CrtP, 9,15,9
-tri-cis ζ-carotene is produced, and this is converted to 9,9
-dicis ζ-carotene, as in Arabidopsis by Z-ISO. Light is also effective for this reaction
(Sugiyama et al. 2020). During desaturation by CrtQ, neurosporene and lycopene are
isomerized to poly-cis forms, and then CrtH isomerizes to all-trans forms. Light is
also effective for their photoisomerization to all-trans forms (Masamoto et al. 2001).
The functions of these enzymes have mainly been confirmed in cyanobacteria, green
algae and land plants (Table 2.2), CrtP and Z-ISO from Arthrospira platensis and