3 Phycobiliproteins in Microalgae: Occurrence …
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COOH
NH 2
O
O
O
CH 2
H
tRNA
OH
N
N
N
N
NH 2
Glutanyl-tRNA
S
CyS
GluTR
tRNAGlu
COOH
O
NH 2
S
Cys
GluTR
NADPH
NADP
+
COOH
H
NH 2
O
- S
CyS
GluTR
Thioester intermediate
Aminolevulinic acid
NH 2
O
H
N
HO
O
N
H
HN
H
N
H
N
O
O
O
O
OH
OH
H
HO
HO
O
OH
O
O
HO
Hydroxymethylbilane
NH H
N
HN
N
H
OH
OH
HO
HO
HO
NH
H
N
HN
N
H
- O
Uroporphyrinogen-III
Coproporphyrinogen
NH
NH HN
HN
OH
Protoporphyrinogen IX
NH
NH HN
HN
N
N
N
N
Protoporphyrin IX
Protoheme
Synthatase
Dehydrogenase
Aminotransferase
Synthatase
Synthatase
Decarboxylase
Oxidase
Oxidase
Fe-chelatase
Fe
OH
OH
HO
O
O
O
O
OH
O
OH
O
O
O
O
HO
O
O
OH
- O
O
O
OH
O
HO O
O
OH
HO
O
O
HO
Porphobilinogen
Fig. 3.2 Biosynthetic pathway from Glutanyl-tRNA to protoheme (Adapted and modified from
Kannaujiya et al. 2017c, Dailey et al. 2017, Pagels et al. 2019)
phyrin IX by oxygen-dependent enzymes. The incorporation of an Mg atom leads to
the formation of protoporphyrin whereas binding of Fe to protoporphyrin IX leads
to the formation of protoheme.