Asparaginase is a bacterial enzyme. The purpose of this enzyme is to reduce the presence of asparagine. Asparagine is a particular amino acid with one goal; to aid the growth of some tumor cells. Therefore, asparaginase is commonly used as a cancer treatment to slow down and shrink tumors. More often than not, it’s included in the drugs used during chemotherapy.
Asparaginase has a crystal structure and is considered a homotetramer. It is believed to have a monomer of at least 330 amino acids - though the exact figure can vary. This monomer comes with a two-domain fold. Both of these domains fit into the alpha/beta class. The N-terminal domain is the bigger of the two. Here, you will find a rare left-handed beta-alpha-beta crossover. This forms a cradle for the active site.
Asparaginase Mechanism & Interactions
Asparaginase catalyzes the hydrolysis of asparagine into aspartic acid and ammonia. In doing so, it reduces asparagine levels in a cell. Asparaginase products are typically cut off from other types of bacteria. They help inhibit protein synthesis in tumor cells. To do this, they deprive the cells of the vital amino acid required to exhibit growth. Tumor cell proliferation is blocked because of the interruption of asparagine-dependent protein synthesis.
This enzyme is seen to be most active during the G1 phase of the cell cycle. In fact, it is said to be a phases specific enzyme when used in drug form. While it can still provide some benefits in other phases, most of the benefits will be seen in G1.
As mentioned previously, asparaginase is primarily used as a cancer treatment. It is injected into the bloodstream during bouts of chemotherapy. It has been used in drug form since 1953 when people first discovered its uses. The reason it’s used is that so many tumor cells depend on a high concentration of asparagine in the blood. They need it to circulate, which provides the tumors with growth. Asparaginase functions to stop this because it converts asparagine. Instead of it flowing through cells and growing tumors, it turns into harmless aspartic acid and ammonia. As a result, the tumor cells don’t just stop growing - they decrease in size. In fact, by using this enzyme, it’s shown to aid in cell death for the tumors.
Asparaginase is also used in the food industry. It is primarily a food processing aid that reduces the amount of acrylamide found in foods. When heated, the amino acid asparagine enters a chemical reaction. Through this, certain carcinogens - like acrylamide - are generated. So, asparaginase is often added to food before it is baked or fried. This then converts the asparagine to aspartic acid and ammonium. Thus, it can’t take part in the chemical reaction, which means it can’t produce carcinogens like acrylamide. It’s impossible to completely remove this carcinogen from food. However, studies show that asparaginase helps reduce it by up to 90% - particularly in starchy foods. It does this without altering the flavor or appearance of the food as well.
So, this enzyme has dual functions, but both revolve around taking asparagine and converting into less harmful things.