What is a Granzyme?

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  • Written By: Jennifer Long
  • Edited By: A. Joseph
  • Last Modified Date: 19 August 2019
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A granzyme, or granule enzyme, is a group of serine proteases that are released by the body’s natural killer cells and cytotoxic T-cells. When cells become infected by viruses, the immune system is triggered. Granzymes are released in order to trigger apoptosis, or programmed cell death, which leads to the destruction of the infected cells. With the problematic cells gone, healing can then begin.

Perforin, which is also called perforin-1, is a type of cytolytic protein that is found in natural killer cells and T-cells. With infected cells, perforin and granulysin work to penetrate the membrane of the infected cells, which creates a pore-like opening. It is this opening that allows the granzyme to enter and destroy the cell from the inside.

Granzyme B, one of the many types of granzymes produced, is believed by many researchers to play an important role in the apoptosis process. Previously, research showed that perforin was the only induction agent that created access holes in infected cells. Newer research suggests that granzyme B works in conjunction with perforin and granulysin to accomplish this goal as part of a protein triple combination.

The multimeric combination created by the granulysin, granzyme B and perforin is also believed to be able to enter infected cells through receptors. The combination is contained in a sac called a vesicle. The perforin allows he granzyme to pass through the surface of the vesicle to the inside of the target cell, and the apoptosis process continues.


Granzymes also have other functions besides contributing to the triggering of apoptosis. They are also involved in activating cytokines and inducing their secretions. Additionally, granzymes aid in regulating the growth of many types of white blood cells, including T-lymphocytes and B-cells.

Measuring the granzyme secretion levels is accomplished in one of two ways. The Western blot technique measures the proteins on a strip with a serum that shows the reaction that will occur. An enzyme-linked immunosorbent assay (ELISA) test uses biochemicals to see how many granzymes are in one sample.

The process of apoptosis does not result in the sudden death of infected cells. It occurs gradually through the life span of the cell. When there are abnormal or infected cells, such as the ones that occur with illnesses and diseases, the cells are resilient to the body’s normal defenses. With the aid of granzymes, these cells can be penetrated to cause the death of the cell sooner. In some cases, this is an important step to preventing the reproduction of infected cells.


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