1. Definition
Guanosine diphosphate (GDP) is a nucleotide that forms when guanosine triphosphate (GTP) loses one phosphate group (due to dephosphorylation by GTPases). It plays a key role in cellular processes by acting as a molecular signal for the inactivation of G-proteins, thereby helping regulate signal transduction and energy transfer in cells.
2. Biochemistry
By splitting off the phosphate residue that is not bound to the sugar molecule, guanosine monophosphate (GMP) is formed, which occurs in the body as a structural component of DNA.
If an additional phosphate residue is attached (with the help of pyruvate kinase) to the unbound phosphate residue, guanosine triphosphate (GTP) is formed.
3. Functions
When an extracellular signal triggers the activation of a G-protein coupled receptor (GPCR), the associated G-protein exchanges its bound GDP for GTP, leading to a conformational change and activation of downstream signaling cascades (see: G-proteins).
Another important process, involving GDP is the Nuclear Import process.
4. Structural formula
Source: https://pubchem.ncbi.nlm.nih.gov/compound/135398619#section=Structures