The Complex Structure and Regulation of Adenylate Cyclase
For over twenty years the adenylate cyclase system has been investigated as a model for hormone action. Situated in the plasma membrane, the enzyme is regulated by a large number of hormones, neurotransmitters, and such “local” hormones as prostaglandins and purinergic compounds. Initially considered to be a two-component system consisting of the catalytic unit (C) and the recognition components (R) for the various hormones and hormone-like substances, a large body of evidence has accumulated that these systems are multisubunit systems composed minimally of R, C, and nucleotide regulatory components (N) that are responsible for the regulation of adenylate cyclase activity by guanine nucleotides [1, 2]. The enzyme is also regulated in opposing manner by sets of Rand N units that either stimulate or inhibit the enzyme. A functional stimulatory receptor unit has been designated as RN., whereas the opposing inhibitory receptor unit has been designated as the RNi unit or complex . Systems displaying dual regulation contain, by definition, both types of receptor complexes. In addition, different R units are often linked structurally to both Ns and Ni in the same cell membrane.
KeywordsAdenylate Cyclase Adenosine Receptor Adenylate Cyclase System Catalytic Unit Adenylate Eyclase
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