Peroxisomes .


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Peroxisomes. Aimee Terauchi and Valerie Villareal. History of Peroxisomes. First observed by electron microscopy in animal cells (1950s), then in plant cells (1960s) Christian deDuve (1965) Isolated from liver cells by centrifugation
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Peroxisomes Aimee Terauchi and Valerie Villareal

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History of Peroxisomes First saw by electron microscopy in creature cells (1950s), then in plant cells (1960s) Christian deDuve (1965) Isolated from liver cells by centrifugation Called them peroxisomes in light of the fact that they produce and annihilate H 2 O 2

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The Peroxisome Single film Roughly circular 0.2 - 1.7 m Composition fluctuates

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Number and Size of Peroxisomes Vary Depending on Environment Glucose constrained More glucose restricted Methanol restricted Hansenula polymorpha cells

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Protein Import C-terminal flag arrangement: SKL N-terminal flag grouping: RLX 5 HL Proteins required in import: peroxins Import driven by ATP hydrolysis Don\'t need to be unfurled for import

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Two Models for Peroxisome Biogenesis

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Metabolic Functions of Peroxisomes Yeasts Biosynthesis : lysine Degradation : amino acids, methanol,  - oxidation of unsaturated fats, deterioration of hydrogen peroxide, glyoxylate cycle Fungi Biosynthesis : penicillin Degradation :  - oxidation of unsaturated fats, decay of hydrogen peroxide, glyoxylate cycle Plants Degradation : purines, a few responses of photorespiration (the transformation of glycolate to glycine and of serine to glycerate),  - oxidation of unsaturated fats, disintegration of hydrogen peroxide, glyoxylate cycle Mammals Biosynthesis : ether phospholipids (plasmalogens), cholesterol and bile acids, polyunsaturated unsaturated fats Degradation : amino acids, purines, prostaglandin, polyamines,  - oxidation of unsaturated fats,  - oxidation of unsaturated fats, decay of hydrogen peroxide Humans Biosynthesis : ether phospholipids (plasmalogens), cholesterol and bile acids, polyunsaturated unsaturated fats Degradation : amino acids, purines,  - oxidation of unsaturated fats,  - oxidation of unsaturated fats, deterioration of hydrogen peroxide

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Major Metabolic Functions of the Peroxisome in Plants -oxidation of unsaturated fats Glyoxylate cycle Photorespiration (Glycolate pathway) Degradation of purines Decomposition of hydrogen peroxide

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Two Types of Peroxisomes in Plants Leaves Catalyzes oxidation of side result of CO 2 obsession in photorespiration Germinating seeds Converts unsaturated fat in seed lipids into sugars required for development in the youthful plant

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Glyoxysomes

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-oxidation happens in mitochondria and peroxisomes in warm blooded animals, however solely in the peroxisome in plants and yeast.

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Glyoxysomes and Leaf Peroxisomes are Interconverted During Development Immunogold particles of 2 sizes bound to: Enzymes of glyoxylate cycle Peroxisomal catalysts a similar populace of peroxisomes expect diverse metabolic parts relying upon formative phase of cotelydon Greening cotelydons

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Photorespiration and Glycolate Oxygenase action of rubisco Consumption of O 2 Glycolate cycle Production of CO 2 Involves 3 organelles (chloroplasts, peroxisomes, & mitochondria)

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The Glycolate Cycle Glycolic corrosive oxidase H 2 O 2 creation

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The Glycolate Cycle

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Purine Degradation Nucleic corrosive purine moieties (adenine and guanine) are debased to uric corrosive xanthine uric corrosive allantoin O 2 H 2 O 2 O 2 H 2 O 2 Xanthine oxidase Urate oxidase Del Rio et al., J. Exper. Plant science 2002

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Urate Oxidase High urate oxidase fixations add to development of crystalline incorporations All purine debasement prompts to uric corrosive

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Oxidases The oxidases utilize sub-atomic oxygen to expel hydrogen particles from particular natural substrates An assortment of mixes, including L-amino acids, D-amino acids, polyamines, methanol, urate, xanthine, and long-chain unsaturated fats, serve as substrates for the diverse oxidases

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Peroxide Detoxification Oxidases utilize O 2 to oxidize natural substances and create hydrogen peroxide (H 2 O 2 ) - e.g., H 2 O 2 produced by glycolate oxidase response, -oxidation of unsaturated fats Peroxisomes likewise contain catalase , the chemical that corrupts H 2 O 2 .

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Importance of H 2 O 2 debasement 2H 2 O 2 2H 2 O + O 2 Peroxisomes contain a high centralization of catalase, a heme protein Other receptive oxygen species (ROS) are shaped in peroxisomes catalase H - O - O - H HO- - OH (?)

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Reactive Oxygen Species Cause harm to lipids, proteins, DNA Amount ROS is decreased by catalase, and superoxide dismutase (SOD) 2O 2 - O 2 + H 2 O 2 • Superoxide anion (radical) Hydrogen peroxide Hydroxyl radical

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Radical Chemistry Initiation: RH + O2 - >R· + ·OH Propagation:  R· + O2 - > · + ROO· + RH - > R· + ROOH- - > RO· + HO· Termination:  R· + R· - > RR R· + ROO·- - > ROOR ROO· + ROO· - > ROOR + O2

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Other Peroxisomal Enzymes

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Conclusions Compartmentalize! To shield the cell from these damaging side effects, such responses are segregated.   

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Peroxisomal Diseases Adrenoleukodystrophy: Deficiency in -oxidation of long-chain unsaturated fats Zellweger disorder: Defect in protein import, offering ascend to "phantom peroxisomes"

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