Dehalogenases, nitroreductases, and peroxidases are important enzyme families. Dehalogenases remove halogen atoms from substrates and are used in bioremediation. Nitroreductases reduce nitro groups on toxic compounds and are important for bioremediation and cancer treatment. Peroxidases catalyze redox reactions using peroxides and have roles in plant metabolism, immune response, and detoxification.

1. Topic :
dehalogenase
nitroreductase
peroxidase
PRESENTED BY
HINA ZAMIR
ROLL # 04

2. Overview
What are they ?
To which family they belong
Where they are present ?
What are their role ?

3. (1) Dehalogenase :
•A dehalogenase is a type of enzyme that
catalyzes the removal of a halogen (cleavage of
carbon-halogen bonds ) atom from a substrate
•EC 3.8 ( hydrolase class )
•Examples include :
•4-chlorobenzoate dehalogenase
•4-chlorobenzoyl-CoA dehalogenase
•Dichloromethane dehalogenase
•Fluoroacetate dehydrogenase
•Haloacetate dehalogenase
•(R)-2-haloacid dehalogenase
•(S)-2-haloacid dehalogenase
•Haloalkane dehalogenase
•Halohydrin dehalogenase
•Haloacetate dehalogenase
•Tetrachloroethene reductive dehalogenase

4. Application
•Halogenated aliphatic compounds
• widely used in agriculture and industries.
• have applications as herbicides, fungicides, insecticides, solvents and hydraulic or transfer fluids
•But now accumulating in the environment
• decontamination by using microbiological degradation methods (transforming them into
harmless products.
• potential use of DEHALOGENASE in biotechnological applications in the bioremediation of
halogenated environmental pollutants
•This enzyme may also have potential applications in the detoxification of contaminated water
•important in dechlorination reactions of chlorinated hydrocarbons

5. (2) nitoreductase
Oxidoreductases family
They form a group of enzymes that have a central role in the reduction of nitro groups on
nitrocompounds using
FMN or FAD (flavin mononucleotide or flavin adenine dinucleotide ) as prosthetic groups and
•NADH or NADPH (nicotinamide adenine dinucleotide or nicotinamide adenine dinucleotide
phosphate ) as reducing agents
•Occurance
•They are primarily found in bacteria, mouse and human .
•This protein is not found in photosynthetic eukaryotes.

6. Categorisation
•nitroreductases have been grouped into two categories based on their ability to reduce nitro
groups in the presence of oxygen by one electron or two-electron transfers
•Type I (oxygen-insensitive) nitroreductases catalyze the sequential transfer of two electrons
from NAD(P)H to the nitro groups of nitrosubstituted compounds, in the presence or absence of
oxygen
•Type II (oxygen-sensitive) nitroreductases catalyze one-electron reductions of the nitro group in
the presence of oxygen,

7. Why important ?
•nitrosubstituted aromatics (reported as toxic, mutagenic, or carcinogenic )
•nitroaromatic compounds an important group of pollutants,
• examples : nitrofurans, nitropyrenes, nitrobenzenes and several others, have been used in
multiple applications as pharmaceuticals, antimicrobial agents, food additives, pesticides,
explosives, dyes and raw materials in several industrial processes. Thus their reduction is
important thus
•Role of nitroreductase
•(1) environmental and human health importance due to their central role in mediating
nitrosubstituted compound toxicity

8. Role of nitroreductase
•(2) biotechnological application for bioremediation , biocatalysis
•Good tool _ It can be used as biosensors and for the bioremediation of nitroaromatic
compounds
•transgenic plants have also been used for the phytoremediation of sites contaminated with high
levels of explosives
•Examples of this include the use of the tobacco plant , Arabidopsis thaliana and Aspen. These
trangenic plants are able to degrade nitroaromatic compounds .
•(3)Clinical significance :
• clinical importance in chemotherapeutic tumor (cancer )treatment, ablation of
specific cells and role in antibiotic resistance

9. (3) Peroxidase
Oxidoreductases: peroxidases (EC 1.11)
can be heam and nonheam proteins
Peroxidase is a heat stable enzyme
Occurance : Peroxidase is usually intracellular, as are the other
fungi and bacteria
In plants : The enzyme occurs in plants like radish, soybean, tomato , potato, turnip,
carrot, wheat, pear, apricot, banana, dates strawberry and horseradish.
In animals :
It has also been found in spleen, lungs, mammary and thyroid glands, bone marrow
and intestine

10. function of peroxidases :
important in redox reactions
Catalyse redox reactions by using a wide variety of donor molecules and reduce a wide range of
peroxides
• example :
H2O2 (peroxide ) + ZH2 (donor) → 2 H2O (reduced ) + Z (oxidized )
"Z" it indicates that the enzyme can use several different molecules as the source of the
hydrogen atoms.

11. Role in Biological Systems :
plants and mammals
Mammmals :
involved in biological processes such as immune system or hormone production or detoxification
detoxification
•Glutathiones ( peroxidases ) present both within and outside cells which use H2O2 or peroxide compounds
of lipids (fats and oils) and remove them
•immune system :
•Peroxidases in the saliva : redox reactions between H2O2 and chemicals called thiocyanates >producing
compounds > kill potentially harmful microorganisms.
•hormone production
•Thyroid peroxidase (TPO ) produced by the thyroid gland which uses iodine ,tyrosine and H202
•Use to create the hormones triiodothyronine (T3) and thyroxine (T4) imp to control metabolism and growth.

12. Role in Biological Systems :
plants and mammals
Plants :
involved in auxin metabolism
suberin formation (wound healing )
cross-linking of cell wall components ( polymerization of macromolecule )
defense against pathogens
.Help in minimizing the damage caused by stress factors or insect pests.
•release of reactive oxygen species (ROS).
•ROS effect can damage or kill cells.
•Role of peroxidases : peroxidases remove ROS, helping prevent damage.

13. In insects
group of insects known as bombardier beetles.
Chamber( mixture of hydrogen peroxide and chemicals called hydroquinones )
When threatened…… they mix these with peroxidases
a redox reaction take place
lot of heat is released, with the resulting liquid ejected explosively at 212°F (100°C). It is a very
effective way of deterring predators

14. Applications :
• Bioremediation of Waste Water: Removal of Phenolic Contaminants
•Removal of Endocrine Disruptive Chemicals (EDCs) that are resistant to conventional waste water treatments
• helpful in removal or degradation of other potent environmental pollutants such as chloroanilines and polycyclic
aromatic hydrocarbons .
Degradation of Polychlorinated Biphenyls (PAHs) Pesticides
Peroxidases extracted from some fungal species have great potential to transform several pesticides into harmless
form
Degradation of Chlorinated Alkanes and Alkenes
Degradation of Chlorinated Dioxins
Degradation of Chlorinated Insecticides
Peroxidase as Biosensors for the continuous monitoring of a contaminated area
Use in Pulp-Paper Industries (lignin degrading & modifying enzyme )

15. Thank You