Protein kinase G (PKG) is a serine/threonine kinase family primarily comprising PKG1 and PKG2 subtypes. These kinases have varied cellular localizations, with PKG1 mainly in the cytoplasm and PKG2 near the cell membrane. Activated by cGMP as a secondary messenger, PKG regulates a wide range of biological processes, including vasodilation, cell proliferation, and apoptosis. Gene expression specificity allows PKG to perform unique functions in different cell types and tissues, whereas genetic mutations may lead to cardiovascular diseases and other health issues.