Autolysis (biology)

In biology, autolysis, more commonly known as self-digestion, refers to the destruction of a cell through the action of its own enzymes. It may also refer to the digestion of an enzyme by another molecule of the same enzyme. The term derives from the Greek αὐτο- ("self") and λύσις ("splitting"). Autolysis is uncommon in living adult organisms and usually occurs in necrotic tissue as enzymes act on components of the cell that would not normally serve as substrates. These enzymes are released due to the cessation of active processes in the cell that provide substrates in healthy, living tissue; autolysis in itself is not an active process. In other words, though autolysis resembles the active process of digestion of nutrients by live cells, the dead cells are not actively digesting themselves as is often claimed, and as the synonym self-digestion suggests. Failure of respiration and subsequent failure of oxidative phosphorylation is the trigger of the autolytic process. The reduced availability and subsequent absence of high-energy molecules that are required to maintain the integrity of the cell and maintain homeostasis causes significant changes in the biochemical operation of the cell. Molecular oxygen serves as the terminal electron acceptor in the series of biochemical reactions known as oxidative phosphorylation that are ultimately responsible for the synthesis of adenosine triphosphate, the main source of energy for otherwise thermodynamically unfavorable cellular processes. Failure of delivery of molecular oxygen to cells results in a metabolic shift to anaerobic glycolysis, in which glucose is converted to pyruvate as an inefficient means of generating adenosine triphosphate. Glycolysis has a lower ATP yield than oxidative phosphorylation and generates acidic byproducts that decrease the pH of the cell, which enables many of the enzymatic processes involved in autolysis. Limited synthesis of adenosine triphosphate impairs many cellular transport mechanisms that utilize ATP to drive energetically unfavorable processes that transport ions and molecules across the cellular membrane.