peroxisome
TRANSCRIPT
Peroxisome
1. History
2. Introduction
3. Location
4. Origin
5. Importance and Functions
6. Disease
7. Conclusion
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
Called them peroxisomes because they generate and destroy H2O2
Number and Size of Peroxisomes
Vary Depending on Environment
Glucose limited More glucose limited Methanol limited
Hansenula polymorpha cells
Peroxisomes are also called Microbodies.
Peroxisomes are about the size of lysosomes (0.5–1.5 µm) and like them are bound by a single membrane. They also resemble lysosomes in being filled with enzymes.
They are round or oval vesicles surrounded by a
phosolipid bilayer
Inside the vesicle are many, many enzymes
Each peroxisome is a single membrane
Each cell contains several hundred peroxisomes
They resemble a lysosome but are not the same
They are self replicating
Size is variable, but it is roughly 700nm
A peroxisome is found in the cytoplasm of a cell
The organ that peroxisomes are most abundant in is
the liver
What they look like
3-10
Peroxisomes Peroxisomes are vesicles than contain enzymes
to oxidize organic substances like fats. In other words the use oxygen to break down molecules.
The enzymes in these organelles produce hydrogen peroxide
Hydrogen peroxide is broken down right away by the enzyme catalase into oxygen and water.
Peroxisomes are abundant in the liver where they produce bile salts and cholesterol and break down fats.
Peroxisome Place into Cytoplasm
Each cell contain 100 or more than peroxisome
Present into both plant and animal
Contain more than 50 Enzymes
Origin
Not well understood
Endosymbiotic
Some scientists believed that they come from bacteria which are parasites
Some other bilieved in Antibacterial origin
Major Metabolic Functions of the Peroxisome in Plants
1. -oxidation of fatty acids
2. Glyoxylate cycle
3. Photorespiration (Glycolate pathway)
4. Degradation of purines
5. Decomposition of hydrogen peroxide
Some of the functions of the
peroxisomes in the human liver: Breakdown (by oxidation) of excess fatty acids.
Breakdown of hydrogen peroxide (H2O2), a potentially dangerous product of fatty-acid oxidation. It is catalyzed by the enzyme catalase.
Participates in the synthesis of cholesterol.
Participates in the synthesis of bile acids.
Participates in the synthesis of the lipids used to make myelin.
Breakdown of excess purines (AMP, GMP) to uric acid.
Two Types of Peroxisomes in Plants
Leaves
Catalyzes oxidation of side product of CO2
fixation in photorespiration
Germinating seeds
Converts fatty acid in seed lipids into sugars
needed for growth in the young plant
Peroxide Detoxification
Oxidases use O2 to oxidize organic substances and
produce hydrogen peroxide (H2O2)
-- e.g., H2O2 generated by glycolate oxidase reaction,
-oxidation of fatty acids
Peroxisomes also contain catalase, the enzyme that
degrades H2O2.
Importance of H2O2 degradation
2H2O2 2H2O + O2
Peroxisomes contain a high concentration of
catalase, a heme protein
Other reactive oxygen species (ROS) are
formed in peroxisomes
catalase
H - - O - - O - -H
HO- -OH (?)
Enzymatic pathways in peroxisomes
Fatty acid oxidation (VLCFA)
H2O2 detoxification (catalase)
Bile acid synthesis
Plasmalogen synthesis
Cholesterol synthesis
Glyoxylate detoxification
Peroxisomal Diseases
Adrenoleukodystrophy: Deficiency in -oxidation of very long- chain fatty acids
Zellweger syndrome: Defect in protein import, giving rise to “ghost peroxisomes”
Adrenoleukodystrophy/ Adrenomyeloneuropathy
Most common peroxisomal disorder (1/20,000)
ALD: progressive neurologic disorder that begins at 5-12 years
Boys with new onset school difficulties & ADHD
Visuo-spatial deficits and hearing loss
Spasticity, ataxia, maybe seizures
Hypoglycemia, salt losing, hyperpigmentation
Zellweger Disorders
Genetic heterogeneity
Dysmorphism (large fontanelle, high forehead, abn ears,
micrognathia, low/broad nose, redundant skin folds)
Neuronal migration disorders and delayed myelination
Seizures
Ocular abnormalities
Liver disease
Death in first year of life
So Finally I conclude that the peroxisome is
the most Abundant Organelle which is maintaing and
controlling the cell functions like biogenesis of amino
acids,cholestorol,purine,plasmalogen etc.