Human Guanylate kinase is the only known enzyme which catalyzes the ATP-dependant phosphorylation of cellular guanosine monophosphate kinase (GMP) into guanosine monophosphate kinase (GDP). Process is crucial for GMP and cyclic guanosine monophosphate (cGMP) recycling, essential for cellular viability and proliferation. It occurs in low eukaryotes, prokaryotes as well as in vertebrates. Human Guanylate kinase is a monomeric protein that is highly conserved and made up of approximately 200 amino acids. This enzyme belongs to the family of transferases with a phosphate group as phosphotransferases. The hGuanylatekinase is essential for producing the nucleotide building blocks of DNA, RNA. That enzyme is indispendable in metabolic activation of antiviral prodrugs. The hGuanylatekinase structure consists of three particular domains that are dynamic: LID, GMP-binding, and CORE domain.