Glicólisis Anaeróbica: Una Vía Energética Clave

Anaerobic Glycolysis: A Key Energy Pathway

Anaerobic glycolysis is a metabolic process that breaks down glucose (C₆H₁₂O₆) into pyruvate (C₃H₄O₃) without the involvement of oxygen, particularly in cells where mitochondria are absent, or oxygen is scarce. This pathway, also known as the Embden-Meyerhof or glycolytic pathway, is an ancient energy source that has persisted in nearly all types of organisms.

Enzymes Involved

Glycolysis involves a series of enzyme-catalyzed reactions, many of which are regulated to control the process. Key enzymes in anaerobic glycolysis include:

• Hexokinase: Converts glucose to glucose-6-phosphate (G6P).
• Phosphofructokinase-1 (PFK1): A pivotal enzyme that regulates the speed of the glycolytic pathway by converting fructose-6-phosphate (F6P) to fructose-1,6-bisphosphate (F1,6BP).
• Pyruvate kinase (PK): Converts phosphoenolpyruvate (PEP) to pyruvate.

Energy Yield

Anaerobic glycolysis results in the production of ATP more quickly than aerobic respiration but is less efficient. For each glucose molecule, anaerobic glycolysis generates only two ATP molecules, while oxidative phosphorylation yields approximately 32 ATP molecules.

Regulation

The rate of anaerobic glycolysis is controlled primarily by phosphofructokinase-1 (PFK1), which is allosterically regulated by ATP, AMP, and citrate levels. High ATP levels inhibit PFK1, while high AMP levels promote it.

Fermentation

Under anaerobic conditions, pyruvate is converted to lactate through the enzyme lactate dehydrogenase, generating two NADH molecules that can be used to regenerate NAD+ for the continuation of glycolysis.

Cells and Tissues Relying on Anaerobic Glycolysis

Anaerobic glycolysis is a critical pathway in cells that lack mitochondria (e.g., erythrocytes) or do not have sufficient oxygen supply. These cells, along with some highly vascularized tissues such as the cornea, lens, and inner medulla of the kidney, rely heavily on anaerobic glycolysis despite the presence of mitochondria.

Clinical Significance

Monitoring lactate levels—a byproduct of anaerobic glycolysis—is useful in clinical settings to assess tissue perfusion and the presence of sepsis, shock, blood loss, anemia, or heart failure.

In summary, anaerobic glycolysis is a critical energy source in cells that lack mitochondria or are oxygen-deprived, providing a quick and less efficient means of producing ATP compared to oxidative phosphorylation. The process is regulated by key enzymes and is a primary energy source in various cells and tissues, such as erythrocytes, the eye's lens, and some regions of the kidney.