PKB enzyme, also known as protein kinase B, is a serine/threonine kinase that plays a crucial role in regulating cell metabolism, cell cycle progression, growth, and survival by phosphorylating numerous cytosolic and nuclear target proteins. In essence, it's a key signaling enzyme within cells that affects many vital processes.
Here's a more detailed breakdown:
- Function: PKB/Akt acts as a central node in various signaling pathways. Once activated, it phosphorylates a wide array of downstream targets.
- Regulation: The activity of PKB/Akt is tightly regulated by upstream signaling molecules, including growth factors, hormones, and other stimuli. This regulation often involves phosphorylation at specific sites on the PKB/Akt protein itself.
- Targets: PKB phosphorylates numerous targets. These include:
- Proteins involved in glucose metabolism, such as GSK-3 (glycogen synthase kinase-3).
- Proteins involved in apoptosis (programmed cell death), such as Bad.
- Proteins involved in cell cycle control.
- Proteins involved in protein synthesis.
- Importance: Because PKB/Akt regulates such fundamental cellular processes, it is implicated in a wide range of diseases, including cancer, diabetes, and cardiovascular disease. Overactivation of the PKB/Akt pathway is frequently observed in cancer cells, contributing to uncontrolled growth and survival.
- Other names: PKB is also commonly referred to as Akt. The three isoforms in mammals are Akt1, Akt2, and Akt3.
In summary, PKB (or Akt) is a vital serine/threonine kinase enzyme involved in controlling cell growth, survival, metabolism, and proliferation by phosphorylating multiple target proteins. Its dysregulation is implicated in many diseases, making it an important therapeutic target.
