Target type: molecularfunction
Catalysis of the reaction: guanosine + phosphate = guanine + D-ribose 1-phosphate. [EC:2.4.2.15]
Guanosine phosphorylase (GP) activity catalyzes the reversible phosphorolysis of guanosine to guanine and ribose-1-phosphate. This reaction involves the cleavage of the N-glycosidic bond between the guanine base and the ribose moiety, with the simultaneous transfer of a phosphate group from inorganic phosphate to the ribose.
Specifically, GP employs a two-step reaction mechanism:
1. **Binding of guanosine:** GP binds guanosine to its active site, where the purine base interacts with specific residues within the enzyme.
2. **Phosphorolysis:** The enzyme utilizes inorganic phosphate to cleave the N-glycosidic bond between guanine and ribose, generating guanine and ribose-1-phosphate. This reaction is reversible, meaning that GP can also catalyze the synthesis of guanosine from guanine and ribose-1-phosphate.
GP plays a critical role in purine metabolism, particularly in the salvage pathway for guanine. It contributes to the interconversion of purine nucleosides and bases, allowing for the recycling of guanine for nucleotide biosynthesis. Additionally, GP activity has been implicated in various cellular processes, including:
- **Immune response:** GP is involved in the regulation of immune responses by influencing the levels of guanine, a key component of purine metabolism.
- **Antimicrobial defense:** Some bacteria rely on GP activity to salvage guanine from their environment, which is crucial for their survival and pathogenicity.
- **Cancer development:** Aberrant GP activity has been linked to tumor growth and metastasis in certain cancers, suggesting its potential as a therapeutic target.
In summary, guanosine phosphorylase activity is a critical enzyme that contributes to the metabolism of guanine and plays a role in various cellular processes, including immune responses, antimicrobial defense, and cancer development.'
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| Protein | Definition | Taxonomy |
|---|---|---|
| Purine nucleoside phosphorylase | [no definition available] | Bos taurus (cattle) |
| Purine nucleoside phosphorylase | A purine nucleoside phosphorylase that is encoded in the genome of human. [PRO:DNx, UniProtKB:P00491] | Homo sapiens (human) |
| Compound | Definition | Classes | Roles |
|---|---|---|---|
| sk&f 29661 | 1,2,3,4-tetrahydroisoquinoline-7-sulfonamide: structure | ||
| 3-deazaguanine | 3-deazaguanine: structure | ||
| adenosine | quinquefolan B: isolated from roots of Panax quinquefolium L.; RN not in Chemline 10/87; RN from Toxlit | adenosines; purines D-ribonucleoside | analgesic; anti-arrhythmia drug; fundamental metabolite; human metabolite; vasodilator agent |
| ly 134046 | LY 134046: RN given refers to parent cpd; structure in first source | ||
| 7,8-dichloro-1,2,3,4-tetrahydroisoquinoline | 7,8-dichloro-1,2,3,4-tetrahydroisoquinoline : A 1,2,3,4-tetrahydroisoquinoline hacing chloro substituents at the 7- and 8-positions. 7,8-dichloro-1,2,3,4-tetrahydroisoquinoline: potent reversible inhibitor of phenylethanolamine N-methyltransferase; structure | isoquinolines; organochlorine compound | |
| 3-deazaguanosine | 3-deazaguanosine: structure | ||
| 4,9-dihydro-7-methoxy-3h-pyrido(3,4b)indole | 4,9-dihydro-7-methoxy-3H-pyrido(3,4b)indole: structure given in first source | ||
| ag 99 | tyrphostin A46: epidermal growth factor-urogastrone receptor antagonist | ||
| galidesivir | |||
| acyclovir | acyclovir : An oxopurine that is guanine substituted by a (2-hydroxyethoxy)methyl substituent at position 9. Used in the treatment of viral infections. Acyclovir: A GUANOSINE analog that acts as an antimetabolite. Viruses are especially susceptible. Used especially against herpes. | 2-aminopurines; oxopurine | antimetabolite; antiviral drug |
| 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 | |
| guanosine | ribonucleoside : Any nucleoside where the sugar component is D-ribose. | guanosines; purines D-ribonucleoside | fundamental metabolite |
| hypoxanthine | nucleobase analogue; oxopurine; purine nucleobase | fundamental metabolite | |
| inosine | inosines; purines D-ribonucleoside | Escherichia coli metabolite; human metabolite; mouse metabolite; Saccharomyces cerevisiae metabolite | |
| 8-amino-9-(2-thienylmethyl)guanine | |||
| allopurinol riboside | allopurinol riboside : A nucleoside analogue that is allopurinol with a beta-D-ribofuranosyl moiety at the 1-position. | nucleoside analogue | metabolite |
| 8-amino-9-benzylguanine | 8-amino-9-benzylguanine: structure given in first source | ||
| forodesine | forodesine: structure in first source | dihydroxypyrrolidine; pyrrolopyrimidine | |
| peldesine | peldesine: potent inhibitor of human CCRF-CEM T-cell proliferation; structure given in first source | ||
| ci 972 | CI 972: structure given in first source | ||
| 8-aminoguanine | |||
| acyclovir monophosphate | |||
| immucillin g | immucillin G: structure in first source | dihydroxypyrrolidine; pyrrolopyrimidine | |
| ulodesine | ulodesine: a purine nucleoside phosphorylase inhibitor | ||
| 9-deazaguanine | |||
| 8-bromoguanosine | purine nucleoside | ||
| 9-deaza-9-(3-thienylmethyl)guanine | |||
| 8-aminoguanosine |