Garman lab: Interconversion of lysosomal enzyme specificities
From Proteopedia
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== Immune Response == | == Immune Response == | ||
| - | Individuals suffering from Fabry disease cannot produce the | + | Individuals suffering from Fabry disease cannot produce the α-GAL protein that is necessary for breaking down Galactose. The usual treatment for this is giving the patient doses of the protein, but this poses a problem. Since the body does not produce the protein, an immune response ranging from severe anaphylaxis to mild discomfort can occur when the patient is given the protein. The body does however produce α-NAGAL, a protein with a similar active site and function as Alpha Gal. Altering the active site of α-NAGAL to match that of α-GAL allows doctors to administer a protein that serves the function of Alpha Gal but has the antigenicity of α-NAGAL, which means the body will recognize the protein and not elicit an immune response. |
== Enzymatic activity == | == Enzymatic activity == | ||
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== Structures shown on this page == | == Structures shown on this page == | ||
| - | 3H54: the enyme | + | 3H54: the enyme α-NAGAL in complex with the sugar GalNAc |
| - | 3HG5: the enyme | + | 3HG5: the enyme α-GAL in complex with the sugar galactose |
| - | 3LX9: the enyme | + | 3LX9: the enyme α-GAL(SA) in complex with the sugar GalNAc |
| - | 3LXA: the enyme | + | 3LXA: the enyme α-GAL(SA) in complex with the sugar galactose |
| - | 3LXC: the enyme | + | 3LXC: the enyme α-GAL(SA) in the presence of glycerol |
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For the animation in Figure 1, the carbon alpha atoms of the shown active site residues were superimposed (RMSD = 0.3 Å). The following views of the active site differences shows a superposition of the six common carbon atoms (RMSD = 0.02 Å) in the bound sugar. It becomes obvious that the sugar is bound in a slightly different orientation with respect to the overall protein structure. | For the animation in Figure 1, the carbon alpha atoms of the shown active site residues were superimposed (RMSD = 0.3 Å). The following views of the active site differences shows a superposition of the six common carbon atoms (RMSD = 0.02 Å) in the bound sugar. It becomes obvious that the sugar is bound in a slightly different orientation with respect to the overall protein structure. | ||
| - | <scene name='78/786673/Bonus/1'> | + | <scene name='78/786673/Bonus/1'>α-GAL active site</scene> |
| - | (use the buttons above to compare with | + | (use the buttons above to compare with α-NAGAL) |
| - | <scene name='78/786673/Bonus/3'> | + | <scene name='78/786673/Bonus/3'>α-GAL overall structure</scene> |
| - | (use the buttons above to compare with | + | (use the buttons above to compare with α-NAGAL) |
| - | Figure 2: Structure of | + | ===Figure 2: Structure of αGAL(SA)=== |
The substitution of Glu 203 and Leu 206 with Serine and alanine reduces the size of the side chain in E203S substitution. The hydrogen bonding of Asp 170 to Tyr 134 or Tyr 207 is altered, thus opening the active site to resemble that of alpha NAGAL. These contribute to the reduced catalytic effect of alpha GAL SA. | The substitution of Glu 203 and Leu 206 with Serine and alanine reduces the size of the side chain in E203S substitution. The hydrogen bonding of Asp 170 to Tyr 134 or Tyr 207 is altered, thus opening the active site to resemble that of alpha NAGAL. These contribute to the reduced catalytic effect of alpha GAL SA. | ||
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<scene name='78/786673/Fig2a_galnac_complex/1'>Panel A</scene>: in complex with GalNAc | <scene name='78/786673/Fig2a_galnac_complex/1'>Panel A</scene>: in complex with GalNAc | ||
| - | Crystal structure of | + | Crystal structure of α-GAL(SA) bound to GalNAc. α-GAL(SA) active site residues are shown in yellow and the product, GalNAc, is shown in gray. The blue frame around GalNAc represents its electron density. Red and blue spheres in the figure represent oxygen and nitrogen, respectively. |
<jmol> | <jmol> | ||
Revision as of 16:04, 3 July 2018
Contents |
How this page was created
The goal of this page is to provide three-dimensional and interactive figures resembling those of an original paper.
Lysosomal storage disease
Lysosomal storage disorders are inherited metabolic diseases characterized by an accumulation of undigested various toxic materials. There are nearly 50 diseases and the two examples shown here are Fabry and Schindler disease. Fabry disease, which occurs between early childhood and adolescence, is characterized by the lack of the enzyme alpha galactosidase (α-Gal). Schindler disease can occur in infancy or in adulthood and is characterized by the lack on the enzyme alpha N-acetylgalactosaminidase (α-NaGal). There are currently no cures for lysosomal storage disorders however enzyme replacement therapy is a treatment option. The basic principle of enzyme replacement therapy is to over express the enzyme of interest heterologously, in this case α-Gal α-NaGal, in a cell line and to isolate and purify it from the culture. In enzyme replacement therapy, patients are injected with the enzymes that they lack in the hopes of restoring the enzymatic activity in their cells.
Immune Response
Individuals suffering from Fabry disease cannot produce the α-GAL protein that is necessary for breaking down Galactose. The usual treatment for this is giving the patient doses of the protein, but this poses a problem. Since the body does not produce the protein, an immune response ranging from severe anaphylaxis to mild discomfort can occur when the patient is given the protein. The body does however produce α-NAGAL, a protein with a similar active site and function as Alpha Gal. Altering the active site of α-NAGAL to match that of α-GAL allows doctors to administer a protein that serves the function of Alpha Gal but has the antigenicity of α-NAGAL, which means the body will recognize the protein and not elicit an immune response.
Enzymatic activity
α-Gal and α-NaGal have relatively identical active sites, which are conserved with the exception of alanine, serine, glutamate and leucine which are positioned differently. The two enzymes have the same folds and both function by cleaving glycosydic bonds however have different substrate specificities. The differences in substrate specificity occur because α-NaGal has a larger binding pocket thus interacting with larger molecules but smaller residues.
Galactose vs. N-acetyl-galactosamine
Structures shown on this page
3H54: the enyme α-NAGAL in complex with the sugar GalNAc
3HG5: the enyme α-GAL in complex with the sugar galactose
3LX9: the enyme α-GAL(SA) in complex with the sugar GalNAc
3LXA: the enyme α-GAL(SA) in complex with the sugar galactose
3LXC: the enyme α-GAL(SA) in the presence of glycerol
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