Guaninenucleotides

Guaninenucleotides are nucleotides that contain the purine guanine as the nucleobase. In cells they exist in three phosphorylated forms—guanosine monophosphate (GMP), guanosine diphosphate (GDP), and guanosine triphosphate (GTP)—as well as their deoxyribonucleotide counterparts found in DNA, dGMP, dGDP, and dGTP. In RNA and DNA, guanine pairs with cytosine through three hydrogen bonds, contributing to the stability and structure of nucleic acids.

Guanine nucleotides play essential roles in metabolism and signaling. GTP is a key energy source and substrate for protein synthesis during translation, and it functions as a regulator in many GTPase enzymes that act as molecular switches. GDP and GTP participate in cellular energy cycles, and the hydrolysis of GTP to GDP releases energy that drives processes such as ribosome translocation, microtubule dynamics, and vesicle trafficking. Guanine nucleotides are also involved in signaling pathways, with GTP- and GDP-bound forms controlling the activity of various signaling proteins; cyclic GMP (cGMP) is a derived second messenger formed from GTP.

Biosynthesis occurs through de novo purine synthesis and salvage pathways. IMP is converted to XMP and then to GMP via GMP synthetase; GMP and its phosphorylated forms are interconverted by various kinases (NDP kinases) to GMP, GDP, and GTP as needed for cellular demand. In DNA replication, the deoxyribonucleotide dGTP is the substrate for incorporation opposite cytosine.

Guanine nucleotides are ubiquitous in nucleic acids and metabolism; disruptions in their synthesis or turnover can have broad biological consequences and are targeted in several pharmacological contexts.