Protein Kinase A

Protein kinase A (PKA) is a group of enzymes whose activity is dependent on the concentration of cAMP, and is also known as cAMP-dependent protein kinase.

Function

Protein kinase A is Protein Kinase A (PKA) helps animals cope with stressful situations. In the "flight or fight" response, muscles become ready for action as a result of the activity of PKA. Upon activation by cAMP, PKA alters the activities of target proteins by phopshorylating specific serine or threonine residues. This enzyme also helps regulate glucose levels. When activated by cAMP, PKA simultaneously catalyzes the breakdown of glycogen and inhibits the synthesis of glucose. PKA also helps regulate glycogen levels, sugar levels, and lipid metabolism.

Structure

PKA consists of two types of subunits. It has a 49-kd regulatory subunit (R) and a 38-kd catalytic subunit (C).When PKA is enzymatically inactive (absence of cAMP), it is a tetrameric complex of a regulatory dimer bound to two catalytic subunits, forming the R2C2 complex. In its active state, the complex dissociates to form an R2 subunit and two C subunits. The catalytic subunit has two lobes. The larger lobe binds the peptide and contributes the key catalytic residues and the smaller lobe makes many contacts with ATP-Mg2+.

Mechanism

Regulation

Disease

Relevance

Structural highlights

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