Target type: molecularfunction
Catalysis of the reaction: GMP + diphosphate = guanine + 5-phospho-alpha-D-ribose 1-diphosphate. [EC:2.4.2.8, GOC:curators]
Guanine phosphoribosyltransferase (GPAT) activity is a crucial metabolic process responsible for the synthesis of guanine monophosphate (GMP) from guanine and phosphoribosyl pyrophosphate (PRPP). This reaction plays a vital role in purine nucleotide metabolism, contributing to the maintenance of cellular pools of GMP, which is an essential building block for DNA and RNA synthesis.
The mechanism involves a two-step process:
1. **Binding of substrates:** GPAT binds both guanine and PRPP at its active site, facilitating their proximity for the reaction to occur.
2. **Phosphoryl transfer:** GPAT catalyzes the transfer of the pyrophosphate group from PRPP to the N9 position of guanine. This results in the formation of GMP and inorganic pyrophosphate.
The reaction is highly specific for guanine, ensuring that only the correct purine base is incorporated into GMP. GPAT exhibits substrate specificity, meaning it preferentially binds to guanine over other purine bases like adenine.
This activity is essential for maintaining a balanced pool of purine nucleotides within the cell, ensuring sufficient GMP availability for nucleic acid synthesis, signal transduction, and other vital cellular processes. Deficiency in GPAT activity can lead to various genetic disorders affecting purine metabolism and ultimately impacting cellular function.'
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| Protein | Definition | Taxonomy |
|---|---|---|
| Hypoxanthine-guanine phosphoribosyltransferase | A hypoxanthine-guanine phosphoribosyltransferase that is encoded in the genome of human. [PRO:DNx, UniProtKB:P00492] | Homo sapiens (human) |
| Compound | Definition | Classes | Roles |
|---|---|---|---|
| chrysene | chrysene : An ortho-fused polycyclic arene found commonly in the coal tar. chrysene: structure in Merck Index, 9th ed, #2252 | ortho-fused polycyclic arene | plant metabolite |
| 6-chrysenamine | 6-chrysenamine: may cause splenic atrophy and leukopenia; minor descriptor (76-84); on-line & Index Medicus search PHENANTHRENES (76-84) | carbopolycyclic compound | |
| 6-nitrochrysene | 6-nitrochrysene: RN given refers to cpd with locant for nitro group in position 6 | carbopolycyclic compound | |
| mercaptopurine | mercaptopurine : A member of the class of purines that is 6,7-dihydro-1H-purine carrying a thione group at position 6. An adenine analogue, it is used in the treatment of acute lymphocytic leukemia (ALL), chronic myeloid leukemia (CML), Crohn's disease, and ulcerative colitis. Mercaptopurine: An antimetabolite antineoplastic agent with immunosuppressant properties. It interferes with nucleic acid synthesis by inhibiting purine metabolism and is used, usually in combination with other drugs, in the treatment of or in remission maintenance programs for leukemia. purine-6-thiol : A thiol that is the tautomer of mercaptopurine. | aryl thiol; purines; thiocarbonyl compound | anticoronaviral agent; antimetabolite; antineoplastic agent |
| thioguanine anhydrous | Thioguanine: An antineoplastic compound which also has antimetabolite action. The drug is used in the therapy of acute leukemia. tioguanine : A 2-aminopurine that is the 6-thiono derivative of 2-amino-1,9-dihydro-6H-purine. Incorporates into DNA and inhibits synthesis. Used in the treatment of leukaemia. | 2-aminopurines | anticoronaviral agent; antimetabolite; antineoplastic agent |
| guanosine monophosphate | guanosine 5'-monophosphate : A purine ribonucleoside 5'-monophosphate having guanine as the nucleobase. Guanosine Monophosphate: A guanine nucleotide containing one phosphate group esterified to the sugar moiety and found widely in nature. | guanosine 5'-phosphate; purine ribonucleoside 5'-monophosphate | biomarker; Escherichia coli metabolite; metabolite; mouse metabolite |
| guanine | 2-aminopurines; oxopurine; purine nucleobase | algal metabolite; Escherichia coli metabolite; human metabolite; mouse metabolite; Saccharomyces cerevisiae metabolite | |
| hypoxanthine | nucleobase analogue; oxopurine; purine nucleobase | fundamental metabolite | |
| inosinic acid | Inosine Monophosphate: Inosine 5'-Monophosphate. A purine nucleotide which has hypoxanthine as the base and one phosphate group esterified to the sugar moiety. | inosine phosphate; purine ribonucleoside 5'-monophosphate | Escherichia coli metabolite; human metabolite; mouse metabolite |
| allopurinol | allopurinol : A bicyclic structure comprising a pyrazole ring fused to a hydroxy-substituted pyrimidine ring. Allopurinol: A XANTHINE OXIDASE inhibitor that decreases URIC ACID production. It also acts as an antimetabolite on some simpler organisms. | nucleobase analogue; organic heterobicyclic compound | antimetabolite; EC 1.17.3.2 (xanthine oxidase) inhibitor; gout suppressant; radical scavenger |
| azaguanine | 8-azaguanine : A triazolopyrimidine that consists of 3,6-dihydro-7H-[1,2,3]triazolo[4,5-d]pyrimidine bearing amino and oxo substituents at positions 5 and 7 respectively. Azaguanine: One of the early purine analogs showing antineoplastic activity. It functions as an antimetabolite and is easily incorporated into ribonucleic acids. | nucleobase analogue; triazolopyrimidines | antimetabolite; antineoplastic agent; EC 2.4.2.1 (purine-nucleoside phosphorylase) inhibitor |