Human Adenine Phosphoribosyltransferase: Purification, Subunit Structure and Substrate Specificity

Thomas, Cornelius B.; Arnold, W; Kelley, William N.

doi:10.1007/978-1-4684-3294-7_4

Cited by 21 publications

(13 citation statements)

References 6 publications

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“…An interesting feature of AICA-based compounds is that they are often used as substrates by enzymes using adeninebased compounds. AICA can serve as a substrate for human adenine phosphoribosyltransferase (19), AICAR is synthesized by the same enzyme that synthesizes AMP (5), and AICAR triphosphate is synthesized from AICAR and PRPP by PRPP synthetase (16), which normally catalyzes the formation of PRPP from ribose-1-phosphate and ATP. This raises the possibility that a novel AICAR derivative produced by rhizobia could mimic or alter the levels of adenine-based cytokinins and thereby influence nodule development.…”

Section: Discussionmentioning

confidence: 99%

Dissection of Nodule Development by Supplementation of Rhizobium leguminosarum biovar phaseoli Purine Auxotrophs with 4-Aminoimidazole-5-Carboxamide Riboside

Newman¹,

Schultz²,

Noel³

1992

Plant Physiol.

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Purine auxotrophs of Rhizobium leguminosarum biovar phaseoli CFN42 elicit uninfected pseudonodules on bean (Phaseolus vulgaris L.). Addition of 4-aminoimidazole-5-carboxamide (AICA) riboside to the root medium during incubation of the plant with these mutants leads to enhanced nodule development, although nitrogenase activity is not detected. Nodules elicited in this manner had infection threads and anatomical features characteristic of normal nodules, such as peripheral vasculature rather than the central vasculature of the pseudonodules that were elicited without AICA riboside supplementation. Although 105 to 106 bacteria could be recovered from these nodules after full development, bacteria were not observed in the interior nodule cells. Instead, large cells with extensive internal membranes were present. Approximately 5% of the normal amount of leghemoglobin and 10% of the normal amount of uricase were detected in these nodules. To promote the development of true nodules rather than pseudonodules, AICA riboside was required no later than the second day through no more than the sixth day following inoculation. After this period, removal of AICA riboside from the root medium did not prevent the formation of true nodules. This observation suggests that there is a critical stage of infection, reached before nodule emergence, at which development becomes committed to forming a true nodule rather than a pseudonodule.

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Section: Discussionmentioning

confidence: 99%

Dissection of Nodule Development by Supplementation of Rhizobium leguminosarum biovar phaseoli Purine Auxotrophs with 4-Aminoimidazole-5-Carboxamide Riboside

Newman¹,

Schultz²,

Noel³

1992

Plant Physiol.

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“…APRT activity in adrenal medulla was found mainly in the cytosolic fraction, as occurs with the enzyme from a great variety of sources. As shown for the enzymes from rat liver (Kenimer et al, 1975) and human erythrocytes (Thomas et al, 1973), APRT from adrenal medulla exhibits initial burst synthesis of AMP, even at 0°C and 1 mM MgC1, and centrifuged at 100,000 g for 60 min to obtain the cytosolic extract (100,000 X g supernatant).…”

Section: Discussionmentioning

confidence: 99%

Purine Nucleotide Synthesis in Adrenal Chromaffin Cells

Rotllán

Miras-Portugal

1985

Journal of Neurochemistry

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The synthesis of purine nucleotides from the salvage precursors adenine and adenosine, and from the de novo precursors formate and glycine, was studied in isolated adrenal chromaffin cells. Both [8-14C]adenine and [8-14C]adenosine from extracellular medium are effectively incorporated into intracellular nucleotides. [14C]Formate and [U-14C]glycine are also incorporated, but de novo synthesis is clearly lower than synthesis from salvage precursors, although similar to de novo synthesis in liver. The enzymes responsible for adenine and adenosine salvage, adenine phosphoribosyltransferase and adenosine kinase, were purified about 1,500-fold. Both enzymes are mainly cytosolic and exhibit a similar molecular weight of around 42,000. The results suggest that chromaffin cells can replenish their intracellular nucleotides lost during the secretory event by an active synthesis from salvage and de novo precursors.

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“…4A) appears not to be sufficient to alter the cytostatic effect of 6-thioguanine. On the other hand, the conversion of 2,6-diaminopurine by APRT was reported to be 10-fold less efficient than that of adenine (Thomas et al, 1973), explaining the decreased cytostatic activity of 2,6-daminopurine after APRT-specific gene knockdown.…”

Section: Phosphoribosylation Of T-705 By Human Hgprtmentioning

confidence: 99%

Role of Human Hypoxanthine Guanine Phosphoribosyltransferase in Activation of the Antiviral Agent T-705 (Favipiravir)

et al. 2013

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6-Fluoro-3-hydroxy-2-pyrazinecarboxamide (T-705) is a novel antiviral compound with broad activity against influenza virus and diverse RNA viruses. Its active metabolite, T-705-ribose-59-triphosphate (T-705-RTP), is recognized by influenza virus RNA polymerase as a substrate competing with GTP, giving inhibition of viral RNA synthesis and lethal virus mutagenesis. Which enzymes perform the activation of T-705 is unknown. We here demonstrate that human hypoxanthine guanine phosphoribosyltransferase (HGPRT) converts T-705 into its ribose-59-monophosphate (RMP) prior to formation of T-705-RTP. The anti-influenza virus activity of T-705 and T-1105 (3-hydroxy-2-pyrazinecarboxamide; the analog lacking the 6-fluoro atom) was lost in HGPRT-deficient Madin-Darby canine kidney cells. This HGPRT dependency was confirmed in human embryonic kidney 293T cells undergoing HGPRT-specific gene knockdown followed by influenza virus ribonucleoprotein reconstitution.Knockdown for adenine phosphoribosyltransferase (APRT) or nicotinamide phosphoribosyltransferase did not change the antiviral activity of T-705 and T-1105. Enzymatic assays showed that T-705 and T-1105 are poor substrates for human HGPRT having K m app values of 6.4 and 4.1 mM, respectively. Formation of the RMP metabolites by APRT was negligible, and so was the formation of the ribosylated metabolites by human purine nucleoside phosphorylase. Phosphoribosylation and antiviral activity of the 2-pyrazinecarboxamide derivatives was shown to require the presence of the 3-hydroxyl but not the 6-fluoro substituent. The crystal structure of T-705-RMP in complex with human HGPRT showed how this compound binds in the active site. Since conversion of T-705 by HGPRT appears to be inefficient, T-705-RMP prodrugs may be designed to increase the antiviral potency of this new antiviral agent.

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Human Adenine Phosphoribosyltransferase: Purification, Subunit Structure and Substrate Specificity

Cited by 21 publications

References 6 publications

Dissection of Nodule Development by Supplementation of Rhizobium leguminosarum biovar phaseoli Purine Auxotrophs with 4-Aminoimidazole-5-Carboxamide Riboside

Dissection of Nodule Development by Supplementation of Rhizobium leguminosarum biovar phaseoli Purine Auxotrophs with 4-Aminoimidazole-5-Carboxamide Riboside

Purine Nucleotide Synthesis in Adrenal Chromaffin Cells

Role of Human Hypoxanthine Guanine Phosphoribosyltransferase in Activation of the Antiviral Agent T-705 (Favipiravir)

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