Adenosylhomocysteinase is an enzyme that acts as a catalyst for S-Adenosylhomocysteine (SAH). Essentially, it converts this into two different products. These products are homocysteine (Hcy) and adenosine (Ado). The process that triggers this transformation is known as reversible hydrolysis. In effect, AHCY also acts as a catalyst to reverse the process as well. This gene is considered a protein coding gene because of this function. It is a competitive inhibitor of S-adenosyl-L-methionine-dependent methyltransferases reactions. As such, AHCY plays a significant role in how methylations are controlled.
The enzyme AHCY contains one very tightly bound NAD+ per subunit. It is also considered to have a crystal structure that forms the gene. The structure of this enzyme is believed to help create a transient oxidation at C-3’ of 5’-deoxyadenosine residue. Therefore, this labilizes the thioether bond.
AHCY Mechanism & Interactions
Naturally, AHCY interacts with SAH. When SAH combines with water, it reacts with Adenosylhomocysteinase. This triggers a natural chemical reaction inside the cell. SAH is then split into two new things. Now, we have homocysteine and adenosine.
Essentially, the AHCY gene is there to offer instructions. The enzyme takes part in a process that involves several steps. These steps basically break down the amino acid (which is a building block of protein) called methionine. Through the reaction that converts SAH to Hcy and Ado, we also see the regulation of other methyl groups. These groups all have one carbon atom and three hydrogen atoms, to other compounds. Methylation is vital for a lot of different processes inside cells. This includes figuring out what instructions in a specific part of DNA are being carried out. It also includes regulating different reactions that include other proteins and lipids. Finally, it is also responsible for the process that chemicals move signals through the nervous system. In effect, it controls how these signals are relayed.
Adenosylhomocysteinase functions to control methylations via regulation of intracellular concentration of adenosylhornocysteine. Effectively, it’s sole purpose is to be the catalyst in a chemical reaction. With AHCY, we wouldn’t be able to convert SAH into Hcy and Ado, then back again. As such, it also helps regulate the levels of SAH throughout the cell. SAH is seen to be critical for a variety of transmethylation reactions. When someone is deficient in AHCY, it’s believed to help cause a disease called hypermethioninemia.
Additionally, research shows three mutations in the Adenosylhomocysteinase gene are present in people suffering from this disease. Any modifications to AHCY are believed to lower the potency of the enzyme. As a result, it can’t provide the proper function that it’s meant to do. In turn, this leads to patients showing signs and symptoms of this health condition. Effectively, this disease is when you have too much methionine in the blood. So, seeing as AHCY is partially responsible for regulating these levels, it’s clear to see how the two link to one another. Consequently, the treatment for this disease often revolves around trying to restore proper function to this enzyme.