Cyclic guanosine monophosphate

  • Guanosine -3 ', 5'-monophosphate
  • Cyclic GMP
  • Cyclic GMP
  • CGMP

Colorless solid

Fixed

Attention

Template: Infobox chemical / molecular formula search available

Cyclic guanosine monophosphate ( cyclic GMP short, cyclic GMP or cGMP ) is a second messenger, a cellular messenger that is responsible for the routing of signals within the cell ( signal transduction). As such he is involved, inter alia, in vision in the rods and cones of the retina, the relaxation of the smooth muscles of blood vessels and the regulation of insulin levels. Most of its effects on signal transduction of cGMP probably develops on cGMP-dependent protein kinase ( protein kinase G).

Biosynthesis and degradation

CGMP is produced from guanosine triphosphate (5'- GTP), an ATP analog. For this conversion, there are at least two forms ( isozymes ) of guanylyl cyclase

  • A is incorporated into the plasma membrane and by the hormones atrial natriuretic peptide (ANP) and BNP stimulated. Hormone - binding site shows to the outside, the cGMP - forming domain inside.
  • The other, there are certain cells in the cytosol. Is a heme protein, which is activated by nitric oxide (NO). During the duration of action of NO is limited ( by oxidation ), its release of nitroglycerin is a slow process.

The cGMP signal is terminated by a phosphodiesterase, which hydrolyzes the second messenger to guanosine monophosphate (5'- GMP).

Function

Which signal is conveyed, depending on the fabric:

  • In the kidney and in the intestine, it regulates ion transport
  • In smooth muscle relaxation and hence it signaled example leads to a dilation of blood vessels ( vasodilation ) and a bronchodilator
  • In the photoreceptor cells (rods ) it increases the influx of sodium ions (Na ) channels by sodium
  • Insulin appears to cAMP and cGMP to control in opposite directions: the cAMP concentration decreases while that of the increases cGMP
  • CGMP may be involved in the development of brain functions

See

Cyclic guanosine monophosphate is an important messenger in visual signal transduction. If some light on the light-sensitive cells, these have high levels of cGMP. This results in the cell membrane to a continuous opening of cGMP - gated ion channels. This limited, the light sensory cell to a decreased membrane potential and their neurotransmitter, glutamate, is distributed constant. This in turn leads to activation of downstream resistant bipolar and ganglion cells of Off- center.

With an increased incidence of light onto the light-sensitive cells in question occur there a structural change of the light-sensitive protein rhodopsin. This structural change via an intermediate step for the activation of phosphodiesterases. Phosphodiesterases are enzymes that degrade cGMP. In the wake of the declining cGMP level close ion channels, it will be paid less glutamate and the postsynaptic nerve cells with off- center are less strongly excited.

When the light sensory cells downstream neurons ( bipolar and ganglion cells ) with On- center of the procedure is reversed.

210746
de