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#detoxification

6 public questions tagged with this topic.

Basics of Cell Biology

Which of the following organelles is involved in detoxification?

Detoxification of endogenous metabolites and exogenous xenobiotics requires oxidative handling and compartmentalization to protect cellular components. Peroxisomes, single membrane organelles containing enzymes imported via peroxisomal targeting signals PTS1 C-terminal SKL tripeptide and PTS2 N-terminal recognized by shuttling receptors PEX5 and PEX7, house acyl-CoA oxidases that beta-oxidize very-long-chain fatty acids C22 and above and branched-chain fatty acids like phytanic acid generating acetyl-CoA for mitochondria plus hydrogen peroxide H2O2 as byproduct. Catalase, core component with h

Ref: Alberts et al., Molecular Biology of the Cell, 7th ed., Chapter 12: Peroxisomes and Detoxification.

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Membrane Transportation

The ABC transporter in plants responsible for detoxification of xenobiotics is found in:

Plants lack animal Na+/K+ gradient but generate proton motive force via plasma membrane P-type H+-ATPase and vacuolar V-type H+-ATPase and pyrophosphatase, driving uptake and compartmentalization of metabolites. Detoxification of xenobiotics, herbicides, and endogenous secondary metabolites employs ATP-binding cassette transporters localized predominantly in vacuolar membrane tonoplast and plasma membrane. Vacuolar ABCC members often called MRP-like transport glutathione S-conjugates, phytochelatin heavy metal complexes, and glucuronide conjugates into vacuole for sequestration, reducing cytos

Ref: Martinoia et al., Planta 2002, Vacuolar transporters; Kang et al., PNAS 2011, ABC in detox.

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Cell Organelles

The major function of peroxisomes is:

Peroxisomes are single membrane oxidative organelles discovered by Rhodin and De Duve, numbering hundreds per cell, containing more than fifty enzymes producing and degrading hydrogen peroxide. Beta-oxidation of very long chain fatty acids greater than twenty two carbons, branched phytanic acid alpha-oxidation, bile acid intermediate shortening and ether lipid synthesis of plasmalogens providing antioxidant membranes and myelin components occur via enzymes acyl-CoA oxidase generating H2O2, bifunctional enzyme and thiolase. Catalase converts two H2O2 to water and oxygen detoxifying, also urate

Ref: Wanders Annu Rev Biochem; peroxisome beta-oxidation VLCFA catalase PTS1 PTS2 Pex import.

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Cell Organelles

The smooth ER plays a crucial role in:

Smooth ER forms anastomosing tubules without ribosomes enriched in enzymes for lipid and xenobiotic metabolism. In hepatocytes it contains cytochrome P450 monooxygenases, NADPH-cytochrome P450 reductase, UDP-glucuronosyltransferases and sulfotransferases that hydroxylate, reduce and conjugate lipophilic drugs, environmental pollutants and endogenous steroids to make them water soluble for biliary or renal excretion. Chronic exposure to phenobarbital induces proliferation of smooth ER increasing detoxification capacity, observed by proliferation of membranes in electron micrographs. Additionall

Ref: Alberts Ch 12; smooth ER CYP450 detoxification, lipid synthesis, SERCA calcium storage, SAR.

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Microbial Physiology

The primary function of glutathione in bacterial stress response is:

Glutathione is a low-molecular-weight tripeptide gamma-glutamyl-cysteinyl-glycine present at millimolar concentrations up to 10 mM in many Gram-negative bacteria such as Escherichia coli and few Gram-positives that synthesize it via GshA and GshB. Reduced form GSH serves as major thiol buffer and electron donor protecting against reactive oxygen species generated continuously by endogenous respiratory electron transport and by host immune oxidative burst involving NADPH oxidase-dependent production of superoxide during phagocytosis. It directly scavenges superoxide anion, hydroxyl radical and

Ref: Prescott's Microbiology, 11th ed., Chapter 7: Glutathione and Oxidative Stress Protection in Bacteria.

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