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Glycosome

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Title: Glycosome  
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Subject: Peroxisome, Glycolysis, Lamina (algae), Axostyle, Cytostome
Collection: Cell Biology, Glycolysis, Organelles
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Glycosome

The glycosome is a proteinaceous matrix. It is believed to have evolved from the peroxisome.[2] This has been verified by work done on Leishmania genetics.[3]

The glycosome is currently being researched as a possible target for drug therapies.

Glycosomes are also found in hepatocytes responsible for storing sugar.[4]

Glycosomes in the trypanosomatid

Contents

  • Structure 1
  • Function 2
    • Glycolysis 2.1
    • Purine Salvage 2.2
  • Evidence 3
    • Microscopic Evidence 3.1
    • Biochemical Evidence 3.2
  • Types 4
    • Lyoglycosomes 4.1
    • Desmoglycosomes 4.2
  • Peroxisome Origin 5
  • Potential Drug Target 6
  • References 7

Structure

Glycosomes are composed of myosin through glycolysis. The glycosomes in the rough and smooth endoplasmic reticulum make use of its glycogen synthase and phosphorylase phosphatases.[1]

Function

Glycosomes function in many processes in the cell. These processes include glycolysis, purine salvage, beta oxidation of fatty acids, and ether lipid synthesis.[5]

Glycolysis

The main function that the glycosome serves is of the glycolytic pathway that is done inside its membrane. By NAD+ for functioning and its regeneration. Fructose 1,6-biphosphate is used in the glycosome as a way to help obtain oxidizing agents to help start glycolysis. The glycosome converts the sugar into 3-phosphoglycerate.[2]

Purine Salvage

Another function of glycosomes is purine salvage. The parasites which have glycosomes present in their cells cannot make purine de novo. This purine that is made in the glycosome is then exported out of the glycosome to be used in the cell in nucleic acid. In other cells the enzymes responsible for this are present in the cytosol. These enzymes found in the glycosome to help with synthesis are guanine and adenine phosphoribosyl transferase, hypoxanthine, and xanthine pho tran. All of these enzymes contain a PTS1 sequence at their carboxyl sequence so that they are sent to the glycosome.[5]

Evidence

Microscopic Evidence

Microscopic techniques have revealed a lot about the glycosome in the cell and have indeed proven that there is a membrane-bound organelle in the cell for glycogen and its processes. Paul Erlich's findings as early as 1883 noted that from the microscope he could tell that glycogen in the cell was always found with what he called a carrier, later known to be protein. The glycogen itself was also always seen in the cell towards the lower pole in one group, fixed. When scientists tried to stain what was assumed was simple glycogen molecules, the staining had different outcomes. This is due to the fact that they weren't free glycogen molecules but really a glycosome. The glycosome was studied in the microscope by examining the glycosome that was stained with uranyl acetate. The U/Pb that was seen stained was the protein that was part of the glycosome. The glycogen in the glycosome in the cells is normally associated with protein that is two to four times the weight of the glycogen. The glycogen itself however, after purified, is found with very little protein, less than three percent normally, showing that the glycosome is responsible and functions by having the proteins and enzymes needed for the glycogen in the glycosome. With the uranyl staining, as an acid, it would cause dissociation of the protein from the glycogen. The glycogen without the protein would form large aggregates and the stain would be the protein. This gives the illusion of glycogen disappearing as it is not stained, but it dissociates from the protein that it is normally associated with in the glycosome.[1]

Biochemical Evidence

There has been a variety of evidence found biochemically to give evidence that glycosomes are present in cells. In the organelle that is assumed to be a glycosome, numerous proteins are found. These include glycogen synthase, phosphorylase, and branching and debranching enzymes for glycogen. All of these are

  1. ^ a b c d e f g Rybicka, Kielan (June 1996). "Glycosomes- the organelles of glycogen metabolism". Tissue and Cell 28 (3): 253–265.  
  2. ^ a b c d Parsons M (2004). "Glycosomes: parasites and the divergence of peroxisomal purpose". Mol Microbiol 53 (3): 717–24.  
  3. ^ Flaspohler, J.A.; Rickoll, W.L.; Beverley, S.M.; Parsons, M. (1997). "Functional identification of a Leishmania gene related to peroxin 2 reveals common ancestry of glycosomes and peroxisomes". Mol. Cell. Biol 17 (3): 1093–1101.  
  4. ^ Elaine, N; Jon Mallat, P B W (2008). Human Anatomy. San Francisco: Benjamin Cummings (Pearson). p. 697. 
  5. ^ a b c Parsons, Marilyn; Furuya, T.; Pal, S.; Kessler, P. (June 2001). "Biogenesis and function of peroxisomes and glycosomes". Molecular and Biochemical Parasitology 115 (1): 19–28.  
  6. ^ White, J (1 July 1999). "Platelet glycosomes". Platelets (Edinburgh) 10 (4): 242–6.  
  7. ^ Galland, Nathalie; de Walque, Voncken, Verlinde, Michels (May 2010). "An internal sequence targets Trypanosoma brucei triosephosphate isomerase to glycosomes". Molecular and Biochemical Parasitology 171 (1): 45–49.  

References

By taking advantage of the pores in the membrane of the glycosome, a drug can enter the organelle and be used to kill the trypanosoma brucei

[7] Unlike peroxisomes, for most of the trypanosomes their glycosomes are needed for them to be able to survive. Because of this need for the glycosome, it has been suggested as a possible drug target to find a

Potential Drug Target

The glycosomes are the most divergent of the different types of organelles stemming from peroxisomes, especially as seen in the genome.[2]

Peroxisome Origin

[1] Desmoglcosomes are not free in the cytosol but rather are with other organelles or structures in the cell. These structures relate to the other organelles mentioned such as the myofibrils, mitochondria, and endoplasmic reticulum. This accounts for why desmoglycosomes are found in

Desmoglycosomes

Lyoglycosomes are glycosomes that are free in the cytosol of the cell. These types of glycosomes are affected by acid. They tend to be less electron dense than the other type of glycosome. Lyoglycosomes also are usually found in chains in the cytosol. Because the lyoglycosomes are not bound to tissue, it is possible to extract these glycosomes with water that is boiling.[1]

Lyoglycosomes

There are two types of glycosomes that are found in cells exhibiting these specialized organelles. These two groups are lyoglycosomes and desmoglycosomes. They differ in their association with other organelles in the cell, along with their relative abundance. Studies have shown that healthy cells have more lyoglycosomes while starved cells have more desmoglycosomes.

Types

[1]

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