About Granzyme / GZM:
Granzymes relates to serine proteases, which cytoplasmic granules will release in the natural killer (NK) cells and cytotoxic cells. Apoptosis, which is programmed cell death, is induced in the target cell by granzymes. Because of this, they eliminate cells that have become infected with bacteria or viruses or are cancerous. Plus, granzymes will also inhibit viral replication and kill bacteria.
In T cells and NK cells, granzymes are filled with cytotoxic granules with perforin. These serine proteases can also be found in the trans-golgi reticulum, Golgi complex, and rough endoplasmic reticulum. The cytotoxic granules and their contents function to stop granzymes entering the target cell cytosol. There is the release of the granules into the immune synapse, where the target cell is formed with them. This is where granzymes are delivered into endosomes in the target cell, with perforin mediating this, and then they will finally be delivered into the target cell cytosol.
As granzymes are part of the family of serine esterase, they are closely linked to the different immune serine proteases that are expressed by innate immune cells, for example, cathepsin G and neutrophil elastase.
There are a number of different types of Granzymes. When it comes to humans, there are five different types of Granzymes that are expressed in humans. This includes Granzyme M, K, H, B, and A. the two Granzyme that have been studied the most are A and B. The reason for this is straightforward, and this is because they are the most abundant.
In recent times, in addition to T lymphocytes, it has been proven that Granzymes are expressed in different immune cell types. Examples include mast cells, B cells, and dendritic cells.
The most abundant serine protease in CD8+ CTLand NK-cytotoxic granules is Granzyme A. There are a number of different functions of this Granzyme. It targets vital proteins for degradation, including several key DNA damage repair proteins, as well as lamins and histones. It also has the purpose of activating a novel programmed cell death pathway, which starts in the mitochondrion and creates reactive oxygen species (ROS). ti does this for the purpose of activating single-stranded DNA damage.
As mentioned, the other type of Granzyme that has been studied considerably is Granzyme B. Granzyme B has the role of activating the intracellular cascade of caspases, which will finally conclude in the target cells being killed. It has other important roles as well. However, it is critical when it comes to target cells being killed in a quick and efficient manner by apoptosis, which is induced by cytotoxic T cell interaction. Granzyme is activated through caspases, especially caspase-3, being activated, which results in many substrates being cleaved.
Hopefully, this gives you a better understanding regarding what Granzymes are, as well as the different roles that they play. Of course, the type of Granzyme will fully dictate the sort of function it has in the human body.