82
monooxygenase (Nishino et al. 2013). The phylogenetic studies of the cytochrome
P450 gene proposed that there is a progenitor proficient to decompose
1,2- dichloroethane, and the studies on neighbouring genes support this. The progenitor may involve ancestral forms of the cytochrome P450 monooxygenase gene
from the same or related pathways. Characterisation of P450 enzymes and manifestation of P450 enzymes in a wide variety of reactions were reviewed by Guengerich
and Munro (2013).
N-alkanes undergo aerobic degradation and usually result in complete mineralisation. The initial step of this degradation involves introduction of the hydroxyl
group and is mediated by the action of alkane hydroxylases. Monooxygenases such
as methane monooxygenase, propane monooxygenase, butane monooxygenase
along with cytochrome p450 alkane hydroxylases and long-chain alkane monooxygenases (LadA) are also involved in the process. For industrial applications longchain monooxygenases are selectively used as they often act as rate-limiting step in
the whole process of biodegradation (Ji et al. 2013).
Arene dioxygenases participate in the cis-dihydroxylation of meta-substituted
phenols (Boyd et al. 2011) and the reaction catalysed by this enzyme resulted in the
formation of cyclohexenone cis-diol metabolites leading to the effective degradation of m-phenol substrates. Candidatus Methylomirabilis oxyfera played an important role in anaerobic waste water treatment and indicated the participation of
dioxygenase, and the enzyme perform nitrite-dependent anaerobic methane oxidation (Luesken et al. 2011).
3.3.2 Laccases
Laccases are multicopper enzymes and uses molecular oxygen as the final electron
acceptor. The enzyme action is much affected by pH and is usually associated with
the degradative removal of many specific pollutants such as polyamines, phenols,
alkenes, diamines aromatic amines, thiols and pesticides. Hence these enzymes are
extensively used in industrial applications such as dye decolourisation, pulp bleaching, effluent detoxification, biosensors and bioremediation (Canas et al. 2007).
The most important application of laccases is in the field of textile industry effluent treatment for bringing decolourisation (Casieri et al. 2008). This is achieved by
the selective decomposition of specific dyes such as malachite green, Azure B,
Bromophenol Blue and Brilliant Blue (Tauber et al. 2008; Guo et al. 2008; Huang
et al. 2007; Camarero et al. 2005).
3.3.3 Peroxidases
Peroxidases have a potential role in the biodegradation of phenols, cresols and chlorinated phenols, paper industry, textile-dye degradation, rhodamine dyes, lignin,
dimethoxybenzene, amines, aromatic alcohols, dioxins, polychlorinated biphenyls,
petroleum hydrocarbons, endocrine disruptive chemicals, herbicides, pesticides and
I.C. Nair and K. Jayachandran
monooxygenase (Nishino et al. 2013). The phylogenetic studies of the cytochrome
P450 gene proposed that there is a progenitor proficient to decompose
1,2- dichloroethane, and the studies on neighbouring genes support this. The progenitor may involve ancestral forms of the cytochrome P450 monooxygenase gene
from the same or related pathways. Characterisation of P450 enzymes and manifestation of P450 enzymes in a wide variety of reactions were reviewed by Guengerich
and Munro (2013).
N-alkanes undergo aerobic degradation and usually result in complete mineralisation. The initial step of this degradation involves introduction of the hydroxyl
group and is mediated by the action of alkane hydroxylases. Monooxygenases such
as methane monooxygenase, propane monooxygenase, butane monooxygenase
along with cytochrome p450 alkane hydroxylases and long-chain alkane monooxygenases (LadA) are also involved in the process. For industrial applications longchain monooxygenases are selectively used as they often act as rate-limiting step in
the whole process of biodegradation (Ji et al. 2013).
Arene dioxygenases participate in the cis-dihydroxylation of meta-substituted
phenols (Boyd et al. 2011) and the reaction catalysed by this enzyme resulted in the
formation of cyclohexenone cis-diol metabolites leading to the effective degradation of m-phenol substrates. Candidatus Methylomirabilis oxyfera played an important role in anaerobic waste water treatment and indicated the participation of
dioxygenase, and the enzyme perform nitrite-dependent anaerobic methane oxidation (Luesken et al. 2011).
3.3.2 Laccases
Laccases are multicopper enzymes and uses molecular oxygen as the final electron
acceptor. The enzyme action is much affected by pH and is usually associated with
the degradative removal of many specific pollutants such as polyamines, phenols,
alkenes, diamines aromatic amines, thiols and pesticides. Hence these enzymes are
extensively used in industrial applications such as dye decolourisation, pulp bleaching, effluent detoxification, biosensors and bioremediation (Canas et al. 2007).
The most important application of laccases is in the field of textile industry effluent treatment for bringing decolourisation (Casieri et al. 2008). This is achieved by
the selective decomposition of specific dyes such as malachite green, Azure B,
Bromophenol Blue and Brilliant Blue (Tauber et al. 2008; Guo et al. 2008; Huang
et al. 2007; Camarero et al. 2005).
3.3.3 Peroxidases
Peroxidases have a potential role in the biodegradation of phenols, cresols and chlorinated phenols, paper industry, textile-dye degradation, rhodamine dyes, lignin,
dimethoxybenzene, amines, aromatic alcohols, dioxins, polychlorinated biphenyls,
petroleum hydrocarbons, endocrine disruptive chemicals, herbicides, pesticides and
I.C. Nair and K. Jayachandran