Chapter 5 - Biotransformation Flashcards
microbial biodegradation of pollutants
- disposal of organic pollutants
- bioremediation
- microbial enzymes in bioremediation
how were organic wastes tradiitionally disposed of?
digging a hole and filling the hole with waste products
difficult to sustain
transfer of organic contaminats from the soil/sediment to another medium (ex. soil to air or soil to water)
physical separation treatment technologies
what was once considered the standard for destruction/removal of organic pollutants?
incineration by thermal oxidation
what issues lead to a greater focus on biological treatment technolgies?
- physical separation treatment technologies
- inceneration
- chemical decomposition
all inefficient
microorganims-mediated transformation or degradation of contaminants into non-hazardous or less-hazardous substances
bioremediation
what is considered effetive bioremediation
microorganisms enzymatically attack the pollutants and convert them to harmless products
what do bacteria rely on for the degradation of organic pollutants?
various intracellular/extracellular enzymes
what are the three classification of bioremediation?
1) biotransformation
2) biodegradation
3) mineralization
the alteration of contaminant molecules into less or nonhazardous molecules
biotransformation
the breakdown of organic substances in smaller organic or inorganic molecules
biodegradation
the complete biodegradation of organic materials into inorganic constituents such as CO2 or H2O4
mineralization
biological catalysts that facilitate the conversion of substrates into products by providing favorable conditions that lower the activation energy of the reaction
enzymes
what are the six major groups of enzymes?
1) oxioreductases
2) transferases
3) hydrolases
4) lysases
5) isomerases
6) ligases (synthetases)
catalyze the trasfer of electrons/protons from a donor to an acceptor
oxioreductases
catalyze the transfer of a functional group from a donor to an acceptor
transferases
facilitate the cleavage of C-C, C-O, C-N, and other bonds by water
hydrolases
catalyze the cleavage of C-C, C-O, and C-N by elimination
lyases
facilitate geometric or structural rearrangement
isomerases
catalyze the joining of two molecules
ligases (synthetases)
mediates detoxification of toxic organic compounds through oxidative coupling
microbial oxioreductases
Microbes assist in the transfer of electrons from a reduced organic substrate (donor) to another chemical compound (acceptor).
microbial oxioreductases
have a major role in the metabolism of organic compounds
* increase their reactivity or water solubility
* bring about cleavage of aromatic ring
* oxidize substrates through the transferring oxygen from molecular oxygen
* broad substrate range /active against a wide range of compounds, including the chlorinated aliphatics
microbial oxygenases
what are the two categorized of microbial oxygenases?
1) monooxygenases
2) dioxygenases
- incorporates 1 atom of oxygen molecule into a substrate
- catalyzes various aromatic and aliphatic compounds’ desulfurization, dehalogenation, denitrification, ammonification, hydroxylation, biotransformation, and biodegradation
monooxygenases
how do monoxygenases act in a mechanism?
adds one oxygen atom to an aromatic ring forming a hydroxyl group
what is an example of a monoxygenase reaction?
n-Alkane to primary alcohol
- introduces 2 oxygen atoms into a substrate
- primarily oxidizes aromatic compounds
- found in soil bacteria and involved in the transformation of aromatic precursors
dioxygenases
how do dioxygenases act in a mechanism?
adds two oxygen atoms to a ring. creates two hydroxyl groups on the aromatic ring.
ring cleavage dioxygenase reacts with the hydroxyl groups and breaks the rings
what is the difference between an intradiol cleavage and an extradiol cleavage?
intradiol: two oxygen atoms react with both hydroxyl groups
extradiol: one oxygen atoms reacts with the hydroxul group and one breaks another C bond
family of oxidases that catalyzes the oxidation of a wide range of reduced phenolic aromatic substrates with molecular oxygen
microbial laccases
catalyzes polymerization processes
* direct degradation
* polymerized pollutants often become insoluble/immobilized = easier removal by sedimentation/filtration/absorption
microbial laccases
what is the general mechanism for phenol oxidation by laccases?
removes hydrogen from one hydroxyl group; removes another hydrogen from the other hydroxul group
polymerization
Used for the decomposition of pollutants, textile dye degradation, lignin degradation, dye decolorization, and sewage treatment
* wastewater treatment
* Some can oxidize PAHS and transform these into more degradable compounds
microbial peroxidases
what is the mechanism for microbial peroxidases?
removes accepts two protons and creates two C=O bonds
What mechanism does this represent?
microbial peroxidase
distrupts major cheical bonds in toxic molecules
* reduces toxicity
* catalyzes several related reactions including condensations and alcoholysis
microbial hydrolytic enzymes
what are some advantages to microbial hydrolytic enzymes?
- readily available
- lack of cofactor
- stereoselectivity
- tolerate the addition of water-miscible solvents
found in bacteria, plant, actinomycetes, and animal cells
* catalyzes breakdown or hydrolysis of fats
* breaks tryglycerides ester bonds in the presence of water
microbial lipases
what is the mechanism for microbial lipases?
removes OCOC17H33 from lipid group in different phases
produced by bacteria, archaea, and fungi. degrades lingocellulosic waste ptoduced by forest and agriculture industries
microbial cellulases
what are the three groups of cellulases?
1) endoglucanase
2) exoglucanase
3) β-glucosidase
creates free chain endes in the hydrolysis process
endoglucanase
removes cellobiose units from the free chain ends
exoglucanase
hydrolyzes cellobiose to glucose units
β-glucosidase
what is the mechanism for microbial cellulases?
breaks off oxygen ester bonds to create individual glucose molecules
products of different categories of cellulases
exo: cellobiose
endo: oligosaccharides of differing sizes
study
what is the most commonly used pesticide?
glyphosphate
what are the four most common pesticides (2008)?
- glyphosphate
- atrazine
- acetochlor
- metolachlor
what are the most common pesticides used in soil?
- linuron
- napropamide
- chloridazon
most common herbicide used in ag, lawn, and garden care
glyphosphate
what is the mode of action for glyphosphate?
- inhibits EPSP synthase
- shikimic acid
modes of resistance for glyphosphate
- sequester in vacuoles
- increases expression os ESPS synthase
- reduced translocation
proposed pathways for oxidation via Aldo-Keto reductase
- EcAKR4-1
- glyphosphate -> glyoxylate
- transaminase
- glycine
- cinnamyl alcohol -> EcAKR4-1 -> cinnamaldehyde
study very hard
agricultural herbicide used in home landscapes
atrazine
mode of action for atrazine
- inhibits Hill reaction in chloroplasts
- plants can no longer produce sugars
transformation of atrazine
- Glutathione S-transferase (GST)
- Cytochrome P450s14 (P450)
study hard
agricultural herbicides used alongside or instead of atrazine
- acetochlor
- metolachlor
mode of action for acetochlor and metolachlor
- inhibits long-chain fatty acids and gibberellin pathway
- inhibits growth of young shoots
transformation of metolachlor
1) Phase I - O-demethylation
2) Phase II - GSH conjugation
3) Phase III - vacuolar transport
4) Phase IV - catabolism
how does S-metolachlor transform into S-metolachlor GSH?
through the action of GSH. phase I to phase II
how is S-metolachlor GSH transported into the vacuole?
ABC transporters. phase III
when S-metalochlor GSH enters the vacuole, what transforms it into S-metolachlor CYS-CLY?
peptidase
what transforms S-metolachlor CYS-GLY into S-metolachlor CYS?
peptidase
mode of action of linuron
- interferes with electron transport of photosystem II
- prevents photosynthesis
- degradation pathways in plants not well-known
- begins with demethylation (P450) in corn, soybean, and crabgrass
linuron
primary mode of breakdown for linuron
- N-alkyl hydroxylation in lupine
- further oxidastion and conjugation within the plant
- mode of action not well understood
- agricultural herbicide
- inhibits root growth
- deradation pathways in plants not well known
napropamide
by-products found in tomatoes from napropamide
hexose conjugates
* 2-N-ethyl propionamide
* 2-N, N-diethyl propionam
modes of resistance for napropamide
- translocate out of roots (tomatoes)
- extensive root systems
mode of action for chloridazon
- interfers with electron transport of photosystem II
- prevents photosynthesis
plants that chloridazon degrades
- soybean
- dwarf bean
- cotton
- sugar beet
in plants, most compounds are stored in ____ or ____ throughout the plant.
lipids; transported
most detox pathways invloved what two enzymes?
- GST
- Cytochrome 450
what are the primary responsibilities for the enzymes GST or cytochrome 450 in detox pathways?
- transform pesticides
- breakdown pesticides: encourage enzyme synthesis
