Final answer:
Kinases and phosphatases are enzymes that add or remove phosphate groups to/from substrates, respectively, regulating various cellular functions. Examples include PKA and PKC which phosphorylate serine or threonine, while phosphofructokinase participates in glycolysis. Their balance is crucial for cell signaling, metabolism, and gene expression.
Step-by-step explanation:
Kinases and phosphatases are enzymes that play critical roles in cellular signaling pathways. Kinases are responsible for the transfer of a phosphate group from a high-energy molecule like ATP to a specific substrate, a process known as phosphorylation. This action often alters the activity of the substrate, such as a protein, thereby regulating cellular processes. On the other hand, phosphatases remove phosphate groups through dephosphorylation, reversing the action of kinases and thus providing a regulatory balance.
For example, PKA (Protein Kinase A) and PKC (Protein Kinase C) are serine-threonine kinases that phosphorylate the amino acids serine or threonine on target proteins. Tyrosine kinases, which are absent in yeasts, add phosphate groups specifically to tyrosine residues, and are crucial for more complex cellular functions seen in multicellular organisms. Proteins like the STAT protein, which can be phosphorylated in a cascade involving kinases, eventually function as transcription factors that control gene expression.
Within cells, kinases like phosphofructokinase and isocitric dehydrogenase function as intracellular enzymes, essential for metabolic pathways such as glycolysis and the citric acid cycle. The balance between kinase and phosphatase activity is essential for proper cellular function, as highlighted by their involvement in numerous intracellular processes including metabolism, signal transduction, and transcriptional regulation.