AP BIOLOGY

Detailed explanation-1: -Protein phosphatase 2A is the major enzyme in brain that dephosphorylates tau protein phosphorylated by proline-directed protein kinases or cyclic AMP-dependent protein kinase.

Detailed explanation-2: -The phosphorylation of a protein can make it active or inactive. Phosphorylation can either activate a protein (orange) or inactivate it (green). Kinase is an enzyme that phosphorylates proteins. Phosphatase is an enzyme that dephosphorylates proteins, effectively undoing the action of kinase.

Detailed explanation-3: -A single enzyme in mammalian skeletal muscle, which has been termed protein phosphatase-1 (6), catalyses the dephosphorylation of phosphorylase, phosphorylase kinase and glycogen synthase, and therefore carries out each of the dephosphorylations which inhibit glycogenolysis or activate glycogen synthesis.

Detailed explanation-4: -Protein kinases are enzymes that transfer a phosphate group from a molecule of ATP onto a protein or other substrate. This activity, known as ‘phosphorylation’, is important for a wide range of cellular processes.

Detailed explanation-5: -Protein phosphatases are the enzymes that hydrolyze phospho-ester bonds in phosphorylated proteins. They play critical roles in cell regulation, given their ability to reverse the effects of protein kinases.