Catalytic subunit of the Serine/Threonine Kinases, cAMP-dependent protein kinases
STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. This subfamily is composed of the cAMP-dependent protein kinases, PKA and PRKX, and similar proteins. The inactive PKA holoenzyme is a heterotetramer composed of two phosphorylated and active catalytic subunits with a dimer of regulatory (R) subunits. Activation is achieved through the binding of the important second messenger cAMP to the R subunits, which leads to the dissociation of PKA into the R dimer and two active subunits. PKA is present ubiquitously in cells and interacts with many different downstream targets. It plays a role in the regulation of diverse processes such as growth, development, memory, metabolism, gene expression, immunity, and lipolysis. PRKX is also reulated by the R subunit and is is present in many tissues including fetal and adult brain, kidney, and lung. It is implicated in granulocyte/macrophage lineage differentiation, renal cell epithelial migration, and tubular morphogenesis in the developing kidney. The PKA-like subfamily is part of a larger superfamily that includes the catalytic domains of other STKs, protein tyrosine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase.
Jiyao W et al.(2023). "The conserved domain database in 2023.",