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==1T0O - a-Galactosidase from Trichoderma reesei and Complex with Galactose==
==Acetylcholinesterase==  
<StructureSection load='1T0O' size='340' side='right' caption='a-Galactosidase complex' scene=''>
<StructureSection load='1B41' size='340' side='right' caption='Acetylcholinesterase' scene=''>
Alpha-Galactosidase is an enzyme found in many different lifeforms.  Enzyme information can be found at <scene name='78/781216/1t0o_alpha-galactosidase/1'>http://www.rcsb.org/structure/1T0O</scene>
Human acetylcholinesterase (AChE) is an enzyme which inhibits the function acetylcholine by way of a rapid hydrolysis.  It is classified as a toxin/ hydrolase and has been linked to things such as snake venom and has been used in the the development of treatment for diseases which involve the nervous system and the transmission of signals to muscles. This specific enzyme has 3 active binding sites and 6 mutations.  Each of which either causing a loss of activity or a mis-folding.


== Function ==
== Function ==
Acetylcholinesterase functions primarily in the synaptic cleft to stop the signal to the neurotransmitter.  This is done by way of a rapid hydrolysis reaction of acetylcholine yielding the products acetate, choline and a hydrogen ion. In conjunction with its biological function it has an unusually high catalytic activity because considering the fact that it is a serine hydrolase it functions more closely to the rate of a limitation by diffusion control.  [1]  A big contributer to the activity of the enzyme is the mutagenesis.  The mutations noted are at positions 234, 365, and 478, these are all also the active sites of the enzyme.  One happens at the acyl ester intermediate, while the other two are at a sort of charge relay system.  The one located in the acyl ester intermediate functions as the main active site.  It is located deep in the gorge lined largely by aromatic residues along with many Serines and this specific sites mutation causes a loss in activity.


a-Galactosidases catalyze the hydrolytic cleavage of the terminal a-galactose residue from many oligosaccharides and polysaccharides.<ref>DOI 10.1074/jbc.M109.060145</ref>  Although humans have lysosomal a-Galactosidase, the enzyme is not generally present in the human digestive tract; as a result, foods that contain raffinose, a carbohydrate broken down by a-Galactosidase, are not digested and passed through the upper intestine until they reach the lower intestine.  There, a-Galactosidase producing bacteria finish the breakdown of it.  Foods that contain raffinose include certain vegetables and legumes, such as beans.  When the bacteria in the lower intestine ferment the carbohydrate, they release gases that can lead to flatulence. Beano is an over-the-counter supplement that contains a-Galactosidase and is promoted to prevent bloating when taken with meals containing raffinose.  The enzyme in Beano is isolated from Aspergillus niger. 
Another structure that contributes greatly to the function of the protein is the ligand binding and interactions of the molecule. It is important to note that there is a high binding affinity for ligands to the structure.  This in turn is what increases the enzymes catalytic rate.   
 
==== Mechanism ====
 
This a-Galactosidase, along with Human a-Galactosidase, reacts via a double displacement mechanism.  Asp132 acts as the nucleophile while Asp226 functions as the acid/base catalyst.<ref>DOI 10.1016/j.jmb.2004.03.062</ref>  a-Galactosidase is part of a group of enzymes known as glycoside hydrolases, which generally have 1 of 2 mechanisms.  The 1st mechanism is a 1 step mechanism that induces the inversion of the stereochemistry of the substrate anomeric center, while the 2nd mechanism is a 2 step mechanism that preserves the stereochemistry.  a-Galactosidase uses the 2-step mechanism. 
 
[[Image:Mechanism_Pic2.png | thumb]]


== Disease ==
== Disease ==
 
As noted above, AChE is known for the blocking the signal of acetylcholine to the synaptic cleft.  It plays important role in neural and muscular functions because it has been linked to neuronal apoptosis.  The disease it is mainly known for being attributed to is Alzheimer's.  Now it does not specifically cause this disease but it has been used to formulate medications and treatments that are already FDA approved.  More so its inhibitor is what is used in the formulation of these treatments.   
Defects in the human a-Galactosidase gene can cause Fabry disease, a lysosomal storage disorder involving buildup of a-galactosylated substrates in tissues.  It is an X-linked inherited disorder that affects 1 in 40,000 males.  It is often characterized by chronic pain, vascular degeneration, cardiac anomalies, as well as other symptoms.  The disease can show different levels of severity correlated with the amount of residual enzymatic activity.  Organs affected can include the eyes, liver, kidney, and heart.  More severe forms generally results from a complete loss of enzymatic activity, while milder phenotypes typically show some enzyme activity.  Most people suffering from Fabry disease have a single point mutation in the gene, and over 400 missense and nonsense mutations have been identified.  Other lysosomal storage disorder include the inherited diseases Tay-Sachs, Sandhoff, and Gaucher diseases.
Recall that acetylcholinesterase is also a toxin.  In a study in which they were testing the effectiveness on mice the venom itself had the toxin.      
 
== Relevance ==
 
These enzymes are found in a variety of organisms, including bacteria, fungi, plants, and animals.  They often function as digestive enzymes.


== Structural highlights ==
== Structural highlights ==
===Scene 1===
This is a view of the <scene name='78/781216/00blue_ligands/2'>protein ligands</scene> that are binding to the enzyme. 
===Scene 2===
These are the <scene name='78/781216/00active_sites/1'>active binding sites</scene>.  They are mutated points however the one deepest in a groove is the primary. 
===Scene 3===
This is the view of <scene name='78/781216/12_mutations/1'>mutations</scene>
===Scene 4===
This is a view of <scene name='78/781216/12_binding_pockets/1'>binding pockets</scene>


This <scene name='78/781216/1t0o_alpha-galactosidase/3'>view</scene> shows the carbohydrate Galactose in the pocket of the active site.  The <scene name='78/781216/1t0o_alpha-galactosidase/11'>two catalytic residues</scene>, Asp132 and Asp226, can be seen sandwiching the inhibitor and product of this enzyme. 


It is also interesting to note that all 5 hydroxyl groups participate in hydrogen bonding with enzyme residues.  Only 5 residues are shown in <scene name='78/781216/1t0o_alpha-galactosidase/7'>this view</scene>, but there are more.
This is a sample scene created with SAT to <scene name="/12/3456/Sample/1">color</scene> by Group, and another to make <scene name="/12/3456/Sample/2">a transparent representation</scene> of the protein. You can make your own scenes on SAT starting from scratch or loading and editing one of these sample scenes.


[[Image:HBond_Pic2.png | thumb]]
</StructureSection>
== References ==
1. Harel M, Kleywegt GJ, Ravelli RB, Silman I, Sussman JL. Crystal structure of an acetylcholinesterase-fasciculin complex: interaction of a three-fingered toxin from snake venom with its target. Structure. 1995 Dec 15;3(12):1355-66. doi: 10.1016/s0969-2126(01)00273-8. PMID: 8747462.


The structure of the enzyme contains <scene name='78/781216/1t0o_alpha-galactosidase/8'>4 N-linked oligosaccharides</scene> comprised of 17 monosaccharides (15 monosaccharides while complexed with galactose). It also contains 2 domains, an <scene name='78/781216/1t0o_alpha-galactosidase/9'>N-terminal domain</scene> that can be described as having an a/B barrel topology, as well as a <scene name='78/781216/1t0o_alpha-galactosidase/10'>C-terminal domain</scene> that has an anti-parallel B-structure.
2. Dvir, H., Silman, I., Harel, M., Rosenberry, T. L., & Sussman, J. L. (2010). Acetylcholinesterase: from 3D structure to function. Chemico-biological interactions, 187(1-3), 10–22. https://doi.org/10.1016/j.cbi.2010.01.042


3. Shafferman, A., Kronman, C., Flashner, Y., Leitner, M., Grosfeld, H., Ordentlich, A., Gozes, Y., Cohen, S., Ariel, N., & Barak, D. (1992). Mutagenesis of human acetylcholinesterase. Identification of residues involved in catalytic activity and in polypeptide folding. The Journal of biological chemistry, 267(25), 17640–17648.


</StructureSection>
== References ==
<references/>
<references/>

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