Which of the following is active in phosphorylated state?
**Core Concept**
The question is testing the understanding of the regulation of enzyme activity through phosphorylation. Phosphorylation is a post-translational modification where a phosphate group is added to a protein, often resulting in a change in the protein's activity or function. This concept is crucial in understanding various cellular processes, including signal transduction pathways.
**Why the Correct Answer is Right**
The correct answer is likely to be a protein kinase, which is an enzyme that transfers phosphate groups to other proteins. Protein kinases are often active in their phosphorylated state, where they can catalyze the transfer of phosphate groups to their target proteins. This process is essential in regulating various cellular processes, including cell signaling, metabolism, and gene expression. The phosphorylation of protein kinases can activate or inhibit their activity, depending on the specific kinase and its target protein.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is likely to be a protein phosphatase, which is an enzyme that removes phosphate groups from proteins. Protein phosphatases are typically active in their dephosphorylated state, where they can catalyze the removal of phosphate groups from their target proteins.
**Option B:** This option is likely to be a protein that is regulated by phosphorylation, but is not a kinase itself. While this protein may be active in its phosphorylated state, it is not the correct answer because it is not an enzyme that phosphorylates other proteins.
**Option D:** This option is likely to be a protein that is not regulated by phosphorylation. While some proteins may be regulated by other post-translational modifications, such as ubiquitination or sumoylation, phosphorylation is not a key regulatory mechanism for this protein.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that protein kinases are often oncogenes when mutated or overexpressed, leading to uncontrolled cell growth and cancer. Understanding the regulation of protein kinases through phosphorylation is crucial in developing targeted therapies for various cancers.
**Correct Answer:** C.