48
V. K. Kannaujiya et al.
an utmost need of an aerobic environment for catalytic regulation of systematic
enzymatic process. Apart from several enzymes, there are few enzymes essentially
required for catalysis of biosynthesis process while other enzymes are regulated in
anaerobic condition. Thus, anaerobic environment would exhibit reduction in biosynthesis of bilins including chlorophylls by mark inhibition in gene expression (Fujita
et al. 2015).
3.5.1 Glutamyl-tRNA to Porphyrin Pathway
Heme (iron-containing porphyrins) is widely distributed among eukaryotic photosynthetic bacteria and certain archaeal species. In a bacterial system, heme compositions
are diverse with different functionality and specific catalytic binding proteins under
diverse environmentally regulated respiratory cytochromes (Mayfield et al. 2011).
However, some non-respiratory-chain cytochromes (P450) are utilizing protoheme
in the form of cofactor to metabolize broad range of substrates by using monooxygenase enzyme (Moody and Loveridge 2014). In photosynthetic bacteria, protoheme
synthesized endogenously is used as substrate for heme oxygenase for synthesis of the
linear tetrapyrrole biliverdin for synthesis of phycobilins (Frankenberg-Dinkel and
Terry 2009). Many bacteria are utilizing heme for release of iron after heme degradation (Runyen-Janecky 2013). The routes of heme sysnthesis start with precursor of
5-aminolevulinate (ALA). The mechanism of synthesis of ALA is widely distributed
in archaea, plants, and most of the bacteria (Jahn et al. 1992). In enzymatic reaction, glutamyl-tRNA is synthesized by glutamyl-tRNA synthetase and converted
into labile intermediates glutamate-1-semialdehyde which is further converted into
ALA by glutamate-1-semialdehyde-2, 1-aminomutase enzyme (GsaM) (Randau
et al. 2004). In the next pathway, ALA is converted into monopyrrole porphobilinogen by catalytic action of porphobilinogen synthase (PbgS). In the series of
transformation, pyrrole building block elements PBG formed macrocyclic uroporphyrinogen III intermediates such as hydroxymethylbilane synthase (HmbS) and
uroporphyrinogen synthase (UroS). In most bacteria, these enzymes are encoded by
genes hemC and hemD (Jordan 1991). The biosynthesis of protoheme is regulated by
siroheme-dependent pathway in archaea, sulfate-reducing, and denitrifying bacteria.
Systematically, protoheme is a result for conversion of uroporphyrinogen III and
coproporphyrinogen III which is catalyzed by uroporphyrinogen III decarboxylase
(Jordan 1990). The coproporphyrin-dependent pathway is generally found in most
of Gram-positive bacteria. Coproporphyrin or protoporphyrin is not found in archaea
and they utilize coproheme intermediate for the synthesis (Kuhner et al. 2014). Now,
coproporphyrinogen III is converted into protoporphyrinogen IX, by decarboxylation mechanism (del Batlle et al. 1965) (Fig. 3.2). This reaction is catalyzed by the
action of coproporphyrinogen decarboxylase in the presence of molecular oxygen
whereas another enzyme coproporphyrinogen dehydrogenase is active in anaerobic
conditions (Layer et al. 2010). Now protoporphyrinogen IX is oxidized to protopor-
V. K. Kannaujiya et al.
an utmost need of an aerobic environment for catalytic regulation of systematic
enzymatic process. Apart from several enzymes, there are few enzymes essentially
required for catalysis of biosynthesis process while other enzymes are regulated in
anaerobic condition. Thus, anaerobic environment would exhibit reduction in biosynthesis of bilins including chlorophylls by mark inhibition in gene expression (Fujita
et al. 2015).
3.5.1 Glutamyl-tRNA to Porphyrin Pathway
Heme (iron-containing porphyrins) is widely distributed among eukaryotic photosynthetic bacteria and certain archaeal species. In a bacterial system, heme compositions
are diverse with different functionality and specific catalytic binding proteins under
diverse environmentally regulated respiratory cytochromes (Mayfield et al. 2011).
However, some non-respiratory-chain cytochromes (P450) are utilizing protoheme
in the form of cofactor to metabolize broad range of substrates by using monooxygenase enzyme (Moody and Loveridge 2014). In photosynthetic bacteria, protoheme
synthesized endogenously is used as substrate for heme oxygenase for synthesis of the
linear tetrapyrrole biliverdin for synthesis of phycobilins (Frankenberg-Dinkel and
Terry 2009). Many bacteria are utilizing heme for release of iron after heme degradation (Runyen-Janecky 2013). The routes of heme sysnthesis start with precursor of
5-aminolevulinate (ALA). The mechanism of synthesis of ALA is widely distributed
in archaea, plants, and most of the bacteria (Jahn et al. 1992). In enzymatic reaction, glutamyl-tRNA is synthesized by glutamyl-tRNA synthetase and converted
into labile intermediates glutamate-1-semialdehyde which is further converted into
ALA by glutamate-1-semialdehyde-2, 1-aminomutase enzyme (GsaM) (Randau
et al. 2004). In the next pathway, ALA is converted into monopyrrole porphobilinogen by catalytic action of porphobilinogen synthase (PbgS). In the series of
transformation, pyrrole building block elements PBG formed macrocyclic uroporphyrinogen III intermediates such as hydroxymethylbilane synthase (HmbS) and
uroporphyrinogen synthase (UroS). In most bacteria, these enzymes are encoded by
genes hemC and hemD (Jordan 1991). The biosynthesis of protoheme is regulated by
siroheme-dependent pathway in archaea, sulfate-reducing, and denitrifying bacteria.
Systematically, protoheme is a result for conversion of uroporphyrinogen III and
coproporphyrinogen III which is catalyzed by uroporphyrinogen III decarboxylase
(Jordan 1990). The coproporphyrin-dependent pathway is generally found in most
of Gram-positive bacteria. Coproporphyrin or protoporphyrin is not found in archaea
and they utilize coproheme intermediate for the synthesis (Kuhner et al. 2014). Now,
coproporphyrinogen III is converted into protoporphyrinogen IX, by decarboxylation mechanism (del Batlle et al. 1965) (Fig. 3.2). This reaction is catalyzed by the
action of coproporphyrinogen decarboxylase in the presence of molecular oxygen
whereas another enzyme coproporphyrinogen dehydrogenase is active in anaerobic
conditions (Layer et al. 2010). Now protoporphyrinogen IX is oxidized to protopor-