The switch is an enzyme called protein kinase G or PKG.

A downstream kinase of the nitric oxide cell signalling pathway, protein kinase G, phosphorylates a small heat shock protein, hsp20.

Cyclic GMP activates protein kinase G, which causes reuptake of Ca and the opening of calcium-activated potassium channels.

Hydralazine increases cyclic guanosine monophosphate (cGMP) levels, increasing the activity of protein kinase G (PKG).

The soluble cGMP activates cyclic nucleotide dependent protein kinase G (PKG or cGKI).

The synthesised cGMP acts as a secondary messenger and activates cGMP-dependent protein kinase (protein kinase G) to regulate cytosolic calcium ion concentration.

For example, PKG (protein kinase G) is a dimer consisting of one catalytic and one regulatory unit, with the regulatory units blocking the active sites of the catalytic units.

Konopacka, Agnieszka, Filip A. Konopacki, and Jan Albrecht (2009) "Protein Kinase G Is Involved in Ammonia-induced Swelling of Astrocytes."

Formation of cGMP initiates several reactions in the body including influence on cGMP ion channels, cGMP binding proteins and protein kinase G (PKG).

The cyclic nucleotides (cGMP and cAMP) produced by these cyclases activate Protein Kinase G and Proten Kinase A and phosphorylate a number of proteins.

In the vascular endothelium, cGMP activates cGMP kinase or PKG (protein kinase G), which is a enzyme that belongs to a type of serine/threonine - specific protein kinase.