About Serine Threonine Protein Kinase / STK:
Serine threonine protein kinases are a group of around 125 protein kinases (of the total 500 enzymes) that phosphorylates the OH group of serine or threonine. They are often referred to as STK while impact various cellular processes within the human body.
Serine Threonine Protein Kinase Structure
Serine protein kinases are also called serine/threonine protein kinases and carry an Enzyme Commission (EC) number of 2.7.11, although some examples do have their individual numbers. Their CAS Registry Number is 9026-43-1.
The STK protein enzymes can include receptor protein serine/threonine kinases (EC 188.8.131.52) Intracellular signaling peptides and proteins such as CK2, protein kinase A, protein kinase C, mitogen-activated protein (MAP) kinases, AKT kinase, Pelle, and Phosphorylase kinase.
Serine/threonine protein kinases enzymes fall into the family of transferases, meaning phosphorylation is used to transfer the oxygen atom of a serine or threonine. A kinase is usually not related to a single substrate because the consensus sequence residues of a target substrate only contact some of the amino acids within the catalytic cleft. The catalytic domain of the kinases is highly conserved,
The serine structure will often follow a HI, NH2, O, OH structure while threonine is H3C, OH, NH2, O, OH. The chemical reactions are expressed as: ATP + a protein ⇌ ADP + a phosphoprotein.
STK Function and Mechanisms
Serine threonine protein kinases is a family o enzymes that covers various substrates, meaning the functions can vary too. Mos/Raf kinases, for example, are activated by growth factors to stimulte cell growth while MAPKs respond to extracellular stimulie to regulate gene expression, mitosis, differentiation, and cell survival.
The AKT serine threonine kinases regulate cell proliferation while the AKT2 is significant for affecting the impact of insulin actions within human cells. Meanwhile, pelle is a self-phosphorylating protein kinase as well as Tube and Toll.
Serine/threonine kinase receptors are integral for embryonic development too, as well as apoptosis and cell differentiation. Most STKs are affected a pseudosubstrate that does not contain the amino acids needed for phosphorylated but still binds to the kinase in a similar manner to a real substrate. Their role in the regulation of these elements, as well as cell growth makes them a hugely significant class of enzymes in the brain and other organs.
Serine Threonine Protein Kinase Interactions
The serine threonine protein kinase is a hugely significant class of protein in relation to cancer as its expression is modified in many types of cancer. Ovarian cancer is one in which some benefits gained from using serine threonine protein kinase inhibitors have been identified, although the impact of those benefits – along with the safety of the procedures – are inconclusive.
P90-kDa ribosomal S6 kinase (the RSK serine protein kinase) has been linked to prostate cancer while new anti-metastatic cancer drugs have been developed to target MAPK as a way to reduce the rate of cell proliferation.
Given that this family of enzymes covers around 25% of the 500 enzymes that affect 30% of all human cells, the serine threonine protein kinase interact with a wide range of receptors and cells.