Guanylate cyclase is a lyase

Lyase

In biochemistry, a lyase is an enzyme that catalyzes the breaking of various chemical bonds by means other than hydrolysis and oxidation, often forming a new double bond or a new ring structure...

 enzyme

Enzyme

Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...

.

Reaction

Guanylate cyclase catalyzes the reaction of guanosine triphosphate

Guanosine triphosphate

Guanosine-5'-triphosphate is a purine nucleoside triphosphate. It can act as a substrate for the synthesis of RNA during the transcription process...

 (GTP) to 3',5'-cyclic guanosine monophosphate (cGMP) and pyrophosphate

Pyrophosphate

In chemistry, the anion, the salts, and the esters of pyrophosphoric acid are called pyrophosphates. Any salt or ester containing two phosphate groups is called a diphosphate. As a food additive, diphosphates are known as E450.- Chemistry :...

:

Types

There are membrane-bound (type 1, guanylate cyclase-coupled receptor

Guanylate cyclase-coupled receptor

Guanylate cyclase-coupled receptor or Membrane-bound guanylyl cyclase is a single transmembrane protein.They are enzyme-linked receptors:* GC-A & GC-B : for natriuretic factors such as atrial natriuretic factor ....

) and soluble (type 2, soluble guanylyl cyclase

Soluble guanylyl cyclase

Soluble guanylyl cyclase is the only known receptor for nitric oxide, NO. It is soluble, i.e. completely intracellular. Most notably, this enzyme is involved in vasodilation...

) forms of guanylyl cyclases. Membrane bound guanylyl cyclases include an external ligand binding domain (e.g., for peptide hormones such as BNP

BNP

-Politics:*Bahujana Nidahas Peramuna, a Sri Lankan political party*Balochistan National Party, a Pakistani political party*Bangladesh Nationalist Party, a Bangladeshi political party*Barbados National Party, a defunct political party in Barbados...

 and ANP

ANP

ANP is a three-letter abbreviation with multiple meanings, as described below:*Adult Nurse Practitioner*Afghan National Police*Acadia National Park*American Nazi Party, an American Neo-Nazi political party....

), a transmembrane domain, and an internal catalytic domain homologous to adenate cyclases . Soluble guanylate cyclase contains a molecule of heme

Heme

A heme or haem is a prosthetic group that consists of an iron atom contained in the center of a large heterocyclic organic ring called a porphyrin. Not all porphyrins contain iron, but a substantial fraction of porphyrin-containing metalloproteins have heme as their prosthetic group; these are...

, and is primariy activated by the binding of nitric oxide (NO) to that heme ). Other activators include YC-1 and carbon monoxide. . See Carbon monoxide#Medicine. The 'soluble' isoforms can be associated with membranes and with large protein assemblies (e.g., at synapses).

Function

Like cAMP, cGMP is an important second messenger that internalizes the message carried by intercellular messengers such as peptide hormones and NO, and can also function as an autocrine signal. Depending on cell type, it can drive adaptive/developmental changes requiring protein synthesis. In smooth muscle, cGMP is the signal for relaxation, and this it is coupled to many homeostaic mechanisms including regulation of vascular and airway tone, insulin secretion, and peristalsis. Once formed, cGMP can be degraded by phosphodiesterase

Phosphodiesterase

A phosphodiesterase is any enzyme that breaks a phosphodiester bond. Usually, people speaking of phosphodiesterase are referring to cyclic nucleotide phosphodiesterases, which have great clinical significance and are described below...

s, which themselves are under different forms of regulation, depending on the tissue.

Like cAMP

Cyclic adenosine monophosphate

Cyclic adenosine monophosphate is a second messenger important in many biological processes...

, cGMP is known to regulate many cellular proteins, such as protein kinase

Protein kinase

A protein kinase is a kinase enzyme that modifies other proteins by chemically adding phosphate groups to them . Phosphorylation usually results in a functional change of the target protein by changing enzyme activity, cellular location, or association with other proteins...

s, ion channel

Ion channel

Ion channels are pore-forming proteins that help establish and control the small voltage gradient across the plasma membrane of cells by allowing the flow of ions down their electrochemical gradient. They are present in the membranes that surround all biological cells...

s, and phosphodiesterases.