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Protein phosphorylation is one of the most common and important post-translational modifications (PTMs), which involves the addition of phosphate groups to specific amino acid residues on proteins. The phosphorylation regulation consists of kinases, phosphatases, and their substrates phospho-binding proteins. Protein phosphorylation is a reversible process that is catalyzed by kinases, whereas the reverse reaction, dephosphorylation, is mediated by phosphatases. Because the phosphate group is highly negatively charged, the phosphorylation of a protein changes its charge and modifies the protein from hydrophobic to hydrophilic polarity, which then alter the conformation and ultimately the functional activity of the protein. A phosphorylated amino acid can bind molecules capable of interacting with other proteins, thereby assembling and detaching protein complexes. In mammals, phosphorylation occurs primarily on serine, threonine, or tyrosine residues.

Protein phosphorylation is a regulatory mechanism that plays an important role in cellular processes such as protein synthesis, signal transduction, cell growth, development, and aging. Many enzymes and receptors are activated or inactivated through phosphorylation/dephosphorylation in response to specific kinases or phosphatases. The signals from the extracellular space or within the cell are driven by the activity of kinases and phosphatases. Protein phosphorylation is therefore a key mechanism by which cells sense their environment and internal metabolic state, enabling individual cells to coordinate appropriate physiological responses in the tissue environment in which they reside. G protein-coupled receptors (GPCRs) are the largest family of signaling proteins that mediate cellular responses to a variety of stimuli, from light to hormones, neurotransmitters, and even extracellular protease activity and calcium. Almost all GPCRS are regulated by phosphorylation, and different phosphorylation patterns on a GPCRs can lead to a range of different signal transduction outcomes. Dysregulation of protein phosphorylation is closely implicated in the occurrence and progression of many diseases such as diabetes, neurodegeneration, autoimmune diseases, and cancers. Therefore, studying protein phosphorylation is important for understanding cell signaling and disease mechanisms.

Methods for detecting phosphorylated proteins include SDS-PAGE, western blot, ELISA, flow cytometry, kinase activity assays, and mass spectrometry (MS). Among them, western blot is the most commonly used method to assess the phosphorylation status of proteins. ELISA is more quantitative than western blot and shows great utility in the study of kinase activity and function. Flow cytometry is one of important methods for the detection of protein phosphorylation, because it allows rapid, quantitative, single-cell analysis. Direct detection of phosphorylated proteins allows for a more detailed analysis of the cellular response to various stimuli than indirect detection methods. Amerigo Scientific offers a wide range of rapid, sensitive, and cost-effective assay kits for the detection of the phosphorylation status of key proteins in biological pathways.