| Modification Notes |
Guanylate cyclases belong to the adenylyl cyclase class-4/guanylyl cyclase family. There are two forms of guanylate cyclase. The soluble form, known as GCS or sGC, act as receptors for nitric oxide. The membrane-bound receptor form, known as GC, are peptide hormone receptors. GCS is a cGMP-synthesizing enzyme, which is the major receptor for the neurotransmitter nitric oxide (NO). It plays a crucial role in smooth muscle contractility, platelet reactivity and neurotransmission. GCS is a heme containing heterodimer, consisting of one å subunit and one ∫ subunit. The heme moeity mediates NO activation, and this heme group also binds carbon monoxide, which weakly stimulates the enzyme. Both NO and CO stimulation are enhanced by the allosteric activator 3-(5'-hydroxymethyl-2'furyl)-benzyl-indazole, YC-1. YC-1 can also stimulate GCS in a NO-independent manner. Both å and ∫ subunits are required for cGMP generation, and at least two isoforms exist for each subunit. Heterodimers consisting of å-1/∫-1 and å-2/∫-1 have been identified, and both display similar enzymatic activity. The distribution of the ∫-2 subunit seems to be much more restricted than the ∫-1 subunit, with predominant expression in kidney and liver. |
