FYBSc Dept of Zoology SMJoshi College Hadapsar Introduction Microbodies were first reported at the ultra structural level in the proximal convoluted tubule of mouse kidney by Rhodin ID: 913875
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Slide1
Microbodies
Tamboli
A.Z.
F.Y.B.Sc.
Dept. of Zoology , S.M.Joshi College, Hadapsar.
Slide2Introduction:
Microbodies
were first reported at the ultra structural level in the proximal convoluted tubule of mouse kidney by
Rhodin
in
1954
.Microbodies are now recognized as ubiquitous subcellular respiratory organelles in eukaryotic cells .
Microbodies
from all tissues appear
morphologically similar
and have
similar enzymatic properties
, but the metabolic pathways within this subcellular compartment vary, depending upon the tissue..
Slide3Microbodies
(
peroxisomes and
glyoxysomes
) were one of the last major subcellular compartments to be recognized, and it was not until the end of the 1960s that their significance was established by several reviews. A
microbody
is a type of organelle that is found in the cells of plants, protozoa, and animals. Organelles in the
microbody
family include
peroxisomes,glyoxysomes
,
glycosomes
and
hydrogenosomes
. In vertebrates,
microbodies
are especially prevalent in the liver and kidney organs
Slide4History:
Microbodies
were first discovered and named in 1954 by
Rhodin
Two years later in 1956
,
Rouiller
and Bernhard
presented the first worldwide accepted images of
microbodies
in liver cells
Then in 1965, Christian
de Duve
and coworkers isolated
microbodies
from the liver of a rat. De Duve also believed that the name
Microbody
was too general and choose the name of
Peroxisome
because of its relationship with hydrogen peroxide .
In
1967,
Breidenbach
and
Beevers
were the first to isolate
microbodies
from plants, which they named
Glyoxysomes
because they were found to contain enzymes of the
Glyoxylate
cycle.
Slide5Morphology
A
microbody
is usually a vesicle with a spherical shape, ranging from 0.2-1.5 micrometers in diameter.
Microbodies
are found in the cytoplasm of a cell, but they are only visible with the use of an electron microscope. They are surrounded by a single phospholipid bilayer membrane and they contain a matrix of intracellular material including enzymes and other proteins, but they do not seem to contain any genetic material to allow them to self-replicate
.
Slide6Microbodies
are morphologically characterized as which are delimited by a single tripartite membrane and contain a finely granular matrix . In liver, an estimation of
1,000
microbodies
per hepatocyte
has been
made.They
show a close spatial relationship to the endoplasmic reticulum. Their catalase can be demonstrated
cytochemically
. Because
microbodies
without inner membranes must be pliable, they usually appear spherical or ovoid, but in the cell they may also be irregular in shape or show unusual projections .
Slide7Fig:Structure
of
Microbody
Slide8T
ypes of
microbodies
There are two types of
microbodies
namely:
Peroxisomes
Glyoxisomes
Slide9Peroxisomes
These (
also called
microbodies
) are organelles found in virtually all eukaryotic cells Called
Peroxisomes
because of their ability to produce or utilize Hydrogen
peroxide.They
are small, oval or spherical in
shape.They
have a fine network of tubules in their
matrix.About
50 enzymes have been identified. The number of enzymes fluctuates according to the function of the cells. These were identified as organelles by the Belgian cytologist Christian
de Duve
in
1967
after they had been first described by a Swedish doctoral student,
J.
Rhodin
in
1954
.
Slide10Slide11However, peroxisomes bud off from the endoplasmic reticulum, not the Golgi apparatus (that is the source of lysosomes). The enzymes and other proteins destined for peroxisomes are synthesized in the cytosol. Each contains a
peroxisomal
targeting signal (PTS) that binds to a receptor molecule that takes the protein into the peroxisome and then returns for another load
.
Slide12Slide13Peroxisomal
diseases
It represent a class of medical conditions caused by defects in peroxisome
functions.This
may be due to defects in single enzymes important for peroxisome function or in
peroxins
, proteins encoded by PEX genes that are critical for normal peroxisome assembly and biogenesis.
Peroxisomal
diseases include:
ALD :
adrenoleukodystrophy
ZS:
Zellweger
syndrome
1.
Adrenoleukodystrophy
Syndrome
Adrenoleukodystrophy
or ALD results in the over-accumulation of very long chain fatty acids or VLCFA and branched chain fatty acids, such as
phytanic
acid. In addition, PBD-ZSD patients show deficient levels of
plasmalogens
, ether-phospholipids necessary for normal brain and lung function
Slide15Slide16Zellweger syndrome
:
also called
cerebrohepatorenal
syndrome
, is a rare congenital disorder characterized by the reduction or absence of functional peroxisomes in the cells of an individual. It is one of a family of disorders called
leukodystrophies
.
Zellweger
syndrome is named after
Hans
Zellweger
(1909–1990), a Swiss-American pediatrician. These are autosomal recessive developmental brain disorders that also result in skeletal and craniofacial
dysmorphism
, liver dysfunction, progressive sensory neural hearing loss, and retinopathy
Slide17Slide18Functions
Peroxisomes perform many functions which include:
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. One of the enzymes involved, HMG-CoA
reductase
, is the target of the popular cholesterol-lowering "statins".
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
Slide20Glyoxisomes
These are specialized peroxisomes found in plants (particularly in the fat storage tissues of germinating seeds) and also in filamentous fungi. As in all peroxisomes, in
glyoxysomes
the fatty acids are hydrolyzed to acetyl-CoA by
peroxisomal
β-oxidation enzymes. Besides
peroxisomal
functions,
glyoxysomes
possess additionally the key enzymes of
glyoxylate
cycle (
isocitrate
lyase
and malate synthase) which accomplish the
glyoxylate
cycle
bypass.Thus
,
glyoxysomes
(as all peroxisomes) contain enzymes that initiate the breakdown of fatty acids and additionally possess the enzymes to produce intermediate products for the synthesis of sugars by gluconeogenesis. The seedling uses these sugars synthesized from fats until it is mature enough to produce them by photosynthesis.
Glyoxysomes
also participate in photorespiration and nitrogen metabolism in root nodules
.
Slide21Slide22