An enzyme, involved in the early steps of purine nucleotide biosynthesis, that catalyzes the formation of 5-phosphoribosylamine from glutamine and phosphoribosylpyrophosphate. EC 2.4.2.14.
The key substance in the biosynthesis of histidine, tryptophan, and purine and pyrimidine nucleotides.
Enzymes of the transferase class that catalyze the transfer of a pentose group from one compound to another.
Purines attached to a RIBOSE and a phosphate that can polymerize to form DNA and RNA.
An enzyme that catalyzes the conversion of 5-phosphoribosyl-1-pyrophosphate and hypoxanthine, guanine, or 6-mercaptopurine to the corresponding 5'-mononucleotides and pyrophosphate. The enzyme is important in purine biosynthesis as well as central nervous system functions. Complete lack of enzyme activity is associated with the LESCH-NYHAN SYNDROME, while partial deficiency results in overproduction of uric acid. EC 2.4.2.8.
A series of heterocyclic compounds that are variously substituted in nature and are known also as purine bases. They include ADENINE and GUANINE, constituents of nucleic acids, as well as many alkaloids such as CAFFEINE and THEOPHYLLINE. Uric acid is the metabolic end product of purine metabolism.

Mutational analysis of Bacillus subtilis glutamine phosphoribosylpyrophosphate amidotransferase propeptide processing. (1/86)

Glutamine phosphoribosylpyrophosphate amidotransferase from Bacillus subtilis is a member of an N-terminal nucleophile hydrolase enzyme superfamily, several of which undergo autocatalytic propeptide processing to generate the mature active enzyme. A series of mutations was analyzed to determine whether amino acid residues required for catalysis are also used for propeptide processing. Propeptide cleavage was strongly inhibited by replacement of the cysteine nucleophile and two residues of an oxyanion hole that are required for glutaminase function. However, significant propeptide processing was retained in a deletion mutant with multiple defects in catalysis that was devoid of enzyme activity. Intermolecular processing of noncleaved mutant enzyme subunits by active wild-type enzyme subunits was not detected in hetero-oligomers obtained from a coexpression experiment. While direct in vitro evidence for autocatalytic propeptide cleavage was not obtained, the results indicate that some but not all of the amino acid residues that have a role in catalysis are also needed for propeptide processing.  (+info)

Methotrexate inhibits the first committed step of purine biosynthesis in mitogen-stimulated human T-lymphocytes: a metabolic basis for efficacy in rheumatoid arthritis? (2/86)

The immunosuppressive and anti-inflammatory effects of low-dose methotrexate (MTX) have been related directly to inhibition of folate-dependent enzymes by polyglutamated derivatives, or indirectly to adenosine release and/or apoptosis and clonal deletion of activated peripheral blood lymphocytes in S-phase. In this study of phytohaemagglutinin-stimulated primary human T-lymphocytes we show that MTX (20 nM to 20 microM) was cytostatic not cytotoxic, halting proliferation at G(1). This stasis of blastogenesis was associated with an inhibition of purine ribonucleotide synthesis but a stimulation of pyrimidine biosynthesis, the normal mitogen-induced expansion of ATP and GTP pools over 72 h being restricted to concentrations of unstimulated T-cells, whereas the increment in UTP pools exceeded that of controls. Decreased incorporation of H(14)CO(3) or [(14)C]glycine into purine ribonucleotides, with no radiolabel accumulation in any de novo synthetic intermediate but enhanced H(14)CO(3) incorporation into UTP, supported these MTX-related effects. Exaggerated [(14)C]hypoxanthine salvage (which normalized the purine and UTP pools) confirmed the increased availability of 5-phosphoribosyl-1-pyrophosphate (PP-ribose-P) as the molecular mechanism underlying these disparate changes. These results provide the first substantive evidence that the immunosuppressive effects of low-dose MTX in primary blasting human T-lymphocytes relate not to the inhibition of the two folate-dependent enzymes of purine biosynthesis but to inhibition of the first enzyme, amidophosphoribosyltransferase, thereby elevating PP-ribose-P and stimulating UTP synthesis. Varying cell types or incubation conditions employed by other workers, especially malignant/activated cells with high basal metabolic rates, might mask the effects noted in primary human T-lymphocytes. The findings imply the involvement of low-dose MTX in the inhibition of T-lymphocyte proliferation and proliferation-dependent processes in rheumatoid arthritis.  (+info)

Purine metabolism in murine virus-induced erythroleukemic cells during differentiation in vitro. (3/86)

Purine metabolism was studied in murine virus-induced erythroleukemia cells stimulated to differentiate in vitro in the presence of dimethylsulfoxide. The activities of the enzymes that catalyze the synthesis of the first intermediate of the de novo purine pathway, phosphoribosyl-1-amine, were decreased while the enzymes that catalyze the conversion of purine bases to purine ribonucleotides remained unchanged at the time the cells acquired the specialized function of hemoglobin synthesis. In addition, cytidine deaminase (cytidine aminohydrolase, EC 3.5.4.5) activity increased with erythropoietic maturation, as it does during murine erythropoiesis in vivo. Stimulation of cellular proliferation of stationary erythroleukemic cells resulted in a marked increase in the activities of purine biosynthetic enzymes. These data provide a convincing example of repression and derepression of the PRA synthesizing enzymes in mammalian cells in vitro, and further evidence that the regulatory mechanisms operative in the normal development of erythrocytes can be activated by exposure of erythroleukemic cells to dimethylsulfoxide.  (+info)

Interdomain signaling in glutamine phosphoribosylpyrophosphate amidotransferase. (4/86)

The glutamine phosphoribosylpyrophosphate (PRPP) amidotransferase-catalyzed synthesis of phosphoribosylamine from PRPP and glutamine is the sum of two half-reactions at separated catalytic sites in different domains. Binding of PRPP to a C-terminal phosphoribosyltransferase domain is required to activate the reaction at the N-terminal glutaminase domain. Interdomain signaling was monitored by intrinsic tryptophan fluorescence and by measurements of glutamine binding and glutamine site catalysis. Enzymes were engineered to contain a single tryptophan fluorescence reporter in key positions in the glutaminase domain. Trp(83) in the glutamine loop (residues 73-84) and Trp(482) in the C-terminal helix (residues 471-492) reported fluorescence changes in the glutaminase domain upon binding of PRPP and glutamine. The fluorescence changes were perturbed by Ile(335) and Tyr(74) mutations that disrupt interdomain signaling. Fluoresence titrations of PRPP and glutamine binding indicated that signaling defects increased the K(d) for glutamine but had little or no effect on PRPP binding. It was concluded that the contact between Ile(335) in the phosphoribosyltransferase domain and Tyr(74) in the glutamine site is a primary molecular interaction for interdomain signaling. Analysis of enzymes with mutations in the glutaminase domain C-terminal helix and a 404-420 peptide point to additional signaling interactions that activate the glutamine site when PRPP binds.  (+info)

Lesions in the nuo operon, encoding NADH dehydrogenase complex I, prevent PurF-independent thiamine synthesis and reduce flux through the oxidative pentose phosphate pathway in Salmonella enterica serovar typhimurium. (5/86)

In Salmonella enterica serovar Typhimurium, PurF-independent thiamine synthesis (or alternative pyrimidine biosynthesis) allows strains, under some growth conditions, to synthesize thiamine in the absence of the first step in the purine biosynthetic pathway. Mutations have been isolated in a number of loci that prevent this synthesis and thus result in an Apb(-) phenotype. Here we identify a new class of mutations that prevent PurF-independent thiamine synthesis and show that they are defective in the nuo genes, which encode the major, energy-generating NADH dehydrogenase of the cell. Data presented here indicated that a nuo mutant has reduced flux through the oxidative pentose phosphate pathway that may contribute to, but is not sufficient to cause, the observed thiamine requirement. We suggest that reduction of the oxidative pentose phosphate pathway capacity in a nuo mutant is an attempt to restore the ratio between reduced and oxidized pyridine nucleotide pools.  (+info)

A purine auxotroph deficient in phosphoribosylpyrophosphate amidotransferase and phosphoribosylpyrophosphate aminotransferase activities with normal activity of ribose-5-phosphate aminotransferase. (6/86)

Three enzyme reactions have been reported to catalyze the synthesis of phosphoribosylamine in eukaryotic cells. These activities are glutamine phosphoribosylpyrophosphate (P-Rib-P-P) amidotransferase [amidophosphoribosyl-transferase; 5-phosphoribosylamine: pyrophosphate phosphoribosyltransferase (glutamate-amidating) EC 2.4.2.14], ammonia P-Rib-P-P aminotransferase, and ammonia ribose-5-phosphate aminotransferase. A purine auxotroph derived from a cell line of Chinese hamster fibroblasts was shown to be deficient in catalytic activities of glutamine P-Rib-P-P amidotransferase and ammonia P-Rib-P-P aminotransferase. Extracts from this cell line had normal ammonia ribose-5-phosphate aminotransferase activity. The defect in purine biosynthesis in the mutant cell line was localized to the synthesis of phosphoribosylamine. These results indicate that glutamine P-Rib-P-P amidotransferase or ammonia P-Rib-P-P aminotransferase or both are important for phosphoribosylamine synthesis, but that ammonia ribose-5-phosphate aminotransferase activity probably does not play a significant role in this eukaryotic cell line. The simultaneous disappearance of both P-Rib-P-P-dependent activities suggests these two enzyme activities are closely related structurally or genetically.  (+info)

Dual role for the glutamine phosphoribosylpyrophosphate amidotransferase ammonia channel. Interdomain signaling and intermediate channeling. (7/86)

Glutamine phosphoribosylpyrophosphate (PRPP) amidotransferase catalyzes the first reaction of de novo purine nucleotide synthesis in two steps at two sites. Glutamine is hydrolyzed to glutamate plus NH(3) at an N-terminal glutaminase site, and NH(3) is transferred through a 20-A hydrophobic channel to a distal PRPP site for synthesis of phosphoribosylamine. Binding of PRPP is required to activate the glutaminase site (termed interdomain signaling) to prevent the wasteful hydrolysis of glutamine in the absence of phosphoribosylamine synthesis. Mutations were constructed to analyze the function of the NH(3) channel. In the wild type enzyme, NH(3) derived from glutamine hydrolysis was transferred to the PRPP site, and little or none was released. Replacement of Leu-415 at the PRPP end of the channel with an alanine resulted in a leaky channel and release of NH(3) to the solvent. Mutations in five amino acids that line the channel and two other residues required for the reorganization of phosphoribosyltransferase domain "flexible loop" that leads to formation of the channel perturbed channel function as well as interdomain signaling. The data emphasize the role of the NH(3) channel in coupling interdomain signaling and NH(3) transfer.  (+info)

Temperature-dependent function of the glutamine phosphoribosylpyrophosphate amidotransferase ammonia channel and coupling with glycinamide ribonucleotide synthetase in a hyperthermophile. (8/86)

Genes encoding glutamine phosphoribosylpyrophosphate amidotransferase (GPAT) and glycinamide ribonucleotide synthetase (GARS) from Aquifex aeolicus were expressed in Escherichia coli, and the enzymes were purified to near homogeneity. Both enzymes were maximally active at a temperature of at least 90 degrees C, with half-lives of 65 min for GPAT and 60 h for GARS at 80 degrees C. GPAT activity is known to depend upon channeling of NH(3) from a site in an N-terminal glutaminase domain to a distal phosphoribosylpyrophosphate site in a C-terminal domain where synthesis of phosphoribosylamine (PRA) takes place. The efficiency of channeling of NH(3) for synthesis of PRA was found to increase from 34% at 37 degrees C to a maximum of 84% at 80 degrees C. The mechanism for transfer of PRA to GARS is not established, but diffusion between enzymes as a free intermediate appears unlikely based on a calculated PRA half-life of approximately 0.6 s at 90 degrees C. Evidence was obtained for coupling between GPAT and GARS for PRA transfer. The coupling was temperature dependent, exhibiting a transition between 37 and 50 degrees C, and remained relatively constant up to 90 degrees C. The calculated PRA chemical half-life, however, decreased by a factor of 20 over this temperature range. These results provide evidence that coupling involves direct PRA transfer through GPAT-GARS interaction rather than free diffusion.  (+info)

Amidophosphoribosyltransferase is an enzyme involved in the metabolic pathway of purine synthesis. Its systematic name is phosphoribosylamine-phosphate transaminase, and it catalyzes the reaction between phosphoribosyl pyrophosphate (PRPP) and glutamine to produce 5-phosphoribosyl-α-[glutamate-1-formimino]-triose phosphate (GAR) and ammonia.

This enzyme plays a crucial role in the biosynthesis of purine nucleotides, which are essential components of DNA, RNA, and many other important molecules in the body. Deficiencies in this enzyme can lead to serious medical conditions, such as Lesch-Nyhan syndrome, a rare genetic disorder characterized by mental retardation, self-mutilation, spasticity, and an excess of uric acid in the blood (hyperuricemia).

Phosphoribosyl Pyrophosphate (PRPP) is defined as a key intracellular nucleotide metabolite that plays an essential role in the biosynthesis of purine and pyrimidine nucleotides, which are the building blocks of DNA and RNA. PRPP is synthesized from ribose 5-phosphate and ATP by the enzyme PRPP synthase. It contributes a phosphoribosyl group in the conversion of purines and pyrimidines to their corresponding nucleotides, which are critical for various cellular processes such as DNA replication, repair, and gene expression. Abnormal levels of PRPP have been implicated in several genetic disorders, including Lesch-Nyhan syndrome and PRPP synthetase superactivity.

Pentosyltransferases are a group of enzymes that catalyze the transfer of a pentose (a sugar containing five carbon atoms) molecule from one compound to another. These enzymes play important roles in various biochemical pathways, including the biosynthesis of nucleotides, glycoproteins, and other complex carbohydrates.

One example of a pentosyltransferase is the enzyme that catalyzes the addition of a ribose sugar to form a glycosidic bond with a purine or pyrimidine base during the biosynthesis of nucleotides, which are the building blocks of DNA and RNA.

Another example is the enzyme that adds xylose residues to proteins during the formation of glycoproteins, which are proteins that contain covalently attached carbohydrate chains. These enzymes are essential for many biological processes and have been implicated in various diseases, including cancer and neurodegenerative disorders.

Purine nucleotides are fundamental units of life that play crucial roles in various biological processes. A purine nucleotide is a type of nucleotide, which is the basic building block of nucleic acids such as DNA and RNA. Nucleotides consist of a nitrogenous base, a pentose sugar, and at least one phosphate group.

In purine nucleotides, the nitrogenous bases are either adenine (A) or guanine (G). These bases are attached to a five-carbon sugar called ribose in the case of RNA or deoxyribose for DNA. The sugar and base together form the nucleoside, while the addition of one or more phosphate groups creates the nucleotide.

Purine nucleotides have several vital functions within cells:

1. Energy currency: Adenosine triphosphate (ATP) is a purine nucleotide that serves as the primary energy currency in cells, storing and transferring chemical energy for various cellular processes.
2. Genetic material: Both DNA and RNA contain purine nucleotides as essential components of their structures. Adenine pairs with thymine (in DNA) or uracil (in RNA), while guanine pairs with cytosine.
3. Signaling molecules: Purine nucleotides, such as adenosine monophosphate (AMP) and cyclic adenosine monophosphate (cAMP), act as intracellular signaling molecules that regulate various cellular functions, including metabolism, gene expression, and cell growth.
4. Coenzymes: Purine nucleotides can also function as coenzymes, assisting enzymes in catalyzing biochemical reactions. For example, nicotinamide adenine dinucleotide (NAD+) is a purine nucleotide that plays a critical role in redox reactions and energy metabolism.

In summary, purine nucleotides are essential biological molecules involved in various cellular functions, including energy transfer, genetic material formation, intracellular signaling, and enzyme cofactor activity.

Hypoxanthine-guanine phosphoribosyltransferase (HGPRT) is an enzyme that plays a crucial role in the salvage pathway of nucleotide synthesis. This enzyme catalyzes the conversion of hypoxanthine and guanine to their respective nucleotides, inosine monophosphate (IMP) and guanosine monophosphate (GMP), by transferring the phosphoribosyl group from 5-phosphoribosyl-1 pyrophosphate (PRPP) to the purine bases.

HGPRT deficiency is a genetic disorder known as Lesch-Nyhan syndrome, which is characterized by mental retardation, self-mutilation, spasticity, and uric acid overproduction due to the accumulation of hypoxanthine and guanine. This disorder is caused by mutations in the HPRT1 gene, leading to a decrease or absence of HGPRT enzyme activity.

Purines are heterocyclic aromatic organic compounds that consist of a pyrimidine ring fused to an imidazole ring. They are fundamental components of nucleotides, which are the building blocks of DNA and RNA. In the body, purines can be synthesized endogenously or obtained through dietary sources such as meat, seafood, and certain vegetables.

Once purines are metabolized, they are broken down into uric acid, which is excreted by the kidneys. Elevated levels of uric acid in the body can lead to the formation of uric acid crystals, resulting in conditions such as gout or kidney stones. Therefore, maintaining a balanced intake of purine-rich foods and ensuring proper kidney function are essential for overall health.

Amidophosphoribosyl transferase at the U.S. National Library of Medicine Medical Subject Headings (MeSH) Human PPAT genome ... Amidophosphoribosyltransferase (ATase), also known as glutamine phosphoribosylpyrophosphate amidotransferase (GPAT), is an ... researchers have suggested that the compound is channeled from Amidophosphoribosyltransferase to GAR synthetase in vivo. Click ... "Molecular cloning of human amidophosphoribosyltransferase". Biochemical and Biophysical Research Communications. 190 (1): 192- ...
Additionally, an alternative transferase mechanism has been evolved by amidophosphoribosyltransferase, which has two active ... family C59 amidophosphoribosyltransferase MEROPS: clan PB, family C44 Subtilisin MEROPS: clan SB, family S8 Prolyl ...
Increased levels of these ribonucleotides may cause feedback inhibition of amidophosphoribosyl transferase, the first and rate- ...
All known Fibro-purF RNAs are found upstream of purF genes, which encode amidophosphoribosyltransferase, which participates in ...
... write AmidoPhosphoRibosylTransferase instead of amidophosphoribosyltransferase. This usage was not widely adopted. Camel case ...
It is the product of the enzyme amidophosphoribosyltransferase which attaches ammonia from glutamine to phosphoribosyl ...
... catalyzed by amidophosphoribosyltransferase, which is activated by PRPP and inhibited by AMP, GMP and IMP. PRPP + L-Glutamine ... researchers have suggested that the compound is channeled from amidophosphoribosyltransferase to GAR synthetase in vivo. PRA + ...
... amidophosphoribosyltransferase EC 2.4.2.15: guanosine phosphorylase EC 2.4.2.16: urate-ribonucleotide phosphorylase EC 2.4.2.17 ...
... amidophosphoribosyltransferase MeSH D08.811.913.400.725.160 - anthranilate phosphoribosyltransferase MeSH D08.811.913.400. ...
... the enzyme amidophosphoribosyltransferase acts upon PRPP to create phosphoribosylamine. The histidine biosynthesis pathway ...
The first enzyme, amidophosphoribosyltransferase, attaches ammonia from glutamine to the ribotide at its anomeric carbon, ...
... amidophosphoribosyltransferase, UDP-N-acetylmuramate dehydrogenase, 50S ribosomal protein L11 methyltransferase, iron-sulphur ...
Amidophosphoribosyl transferase at the U.S. National Library of Medicine Medical Subject Headings (MeSH) Human PPAT genome ... Amidophosphoribosyltransferase (ATase), also known as glutamine phosphoribosylpyrophosphate amidotransferase (GPAT), is an ... researchers have suggested that the compound is channeled from Amidophosphoribosyltransferase to GAR synthetase in vivo. Click ... "Molecular cloning of human amidophosphoribosyltransferase". Biochemical and Biophysical Research Communications. 190 (1): 192- ...
Amidophosphoribosyltransferase (ATase) (EC 2.4.2.14) (Glutamine phosphoribosylpyrophosphate amidotransferase) 17295914, ... MSMEG_5800 MSMEG_5800 Amidophosphoribosyltransferase (ATase) (EC 2.4.2.14) (Glutamine phosphoribosylpyrophosphate ...
... amidophosphoribosyltransferase, 2.4.2.14; phosphoribosylamine-glycine ligase, 6.3.4.13; phosphoribosylglycinamide ...
CDS with a similar description: amidophosphoribosyltransferase glutamine phosphoribosylpyrophosphate amidotransferase ATASE ... amidophosphoribosyltransferase (glutamine phosphoribosylpyrophosphate amidotransferase; ATASE; GPATase). NC_017501:1633436: ...
2.4.2.14Name: amidophosphoribosyltransferase. Other names: phosphoribosyldiphosphate 5-amidotransferase, glutamine ...
... amidophosphoribosyltransferase; DHFR, dihydrofolate reductase; FA, folic acid; FH2, dihydrofolate; FH4, tetrahydrofolate; FPGH ... amidophosphoribosyltransferase; DHFR, dihydrofolate reductase; FA, folic acid; FH2, dihydrofolate; FH4, tetrahydrofolate; FPGH ...
... amidophosphoribosyltransferase (ATASE), 5'-nucleotidase (5NUC), and the xanthine oxidase/dehydrogenase (XD) reactions. The ...
... that regulation of purine synthesis de novo is effected at both the PP-Rib-P synthetase and amidophosphoribosyltransferase ...
Amidophosphoribosyltransferase Preferred Term Term UI T001766. Date01/01/1999. LexicalTag NON. ThesaurusID NLM (1975). ... Glutamine-Amidophosphoribosyltransferase Term UI T001768. Date02/03/1982. LexicalTag NON. ThesaurusID UNK (19XX). ... Amidophosphoribosyltransferase Preferred Concept UI. M0000902. Registry Number. EC 2.4.2.14. Related Numbers. 9031-82-7. Scope ... Amidophosphoribosyltransferase. Tree Number(s). D08.811.913.400.725.130. Unique ID. D000582. RDF Unique Identifier. http://id. ...
Amidophosphoribosyltransferase Preferred Term Term UI T001766. Date01/01/1999. LexicalTag NON. ThesaurusID NLM (1975). ... Glutamine-Amidophosphoribosyltransferase Term UI T001768. Date02/03/1982. LexicalTag NON. ThesaurusID UNK (19XX). ... Amidophosphoribosyltransferase Preferred Concept UI. M0000902. Registry Number. EC 2.4.2.14. Related Numbers. 9031-82-7. Scope ... Amidophosphoribosyltransferase. Tree Number(s). D08.811.913.400.725.130. Unique ID. D000582. RDF Unique Identifier. http://id. ...
Deficiency of amidophosphoribosyltransferase (disorder). Code System Preferred Concept Name. Deficiency of ...
Amidophosphoribosyltransferase; Converts the free carboxyl group of a malonyl-thioester to its methyl ester by transfer of a ... Amidophosphoribosyltransferase; Converts the free carboxyl group of a malonyl-thioester to its methyl ester by transfer of a ... Amidophosphoribosyltransferase; Converts the free carboxyl group of a malonyl-thioester to its methyl ester by transfer of a ... Amidophosphoribosyltransferase; Converts the free carboxyl group of a malonyl-thioester to its methyl ester by transfer of a ...
amidophosphoribosyltransferase activity. IEP. Neighborhood. CC. GO:0005634. nucleus. IEP. Neighborhood. BP. GO:0006144. purine ...
Amidophosphoribosyltransferase (EC 2.4.2.14). Position: -246. Score: 9.8. Sequence: ATTAAACT-(3)-CTTAAATT-(3)-GTTAAATA ...
Amidophosphoribosyltransferase - Preferred Concept UI. M0000902. Scope note. An enzyme, involved in the early steps of purine ... Amidophosphoribosyltransferase Entry term(s). 5-Amidotransferase, Phosphoribosyldiphosphate Amidotransferase, Phosphoribosyl ... Amidophosphoribosyltransferase Entry term(s):. 5-Amidotransferase, Phosphoribosyldiphosphate. Amidotransferase, Phosphoribosyl ... Glutamine Amidophosphoribosyltransferase Glutamine Phosphoribosyl Pyrophosphate Amidotransferase Glutamine- ...
Amidophosphoribosyltransferase. 1 Select filter option. Antigen peptide transporter 1. 1 Select filter option. Antigen peptide ...
C45562 Q06203 Amidophosphoribosyltransferase C118617 P21397 Amine Oxidase [Flavin-Containing] A C125505 P27338 Amine Oxidase [ ...
T001767Glutamine Phosphoribosyl Pyrophosphate Amidotransferase T001768Glutamine Amidophosphoribosyltransferase T001768Glutamine ...
476546 1.22 amidophosphoribosyltransferase precursor Ppat Rattus norvegicus N/A P35433.1 ...
Amidophosphoribosyltransferase Amifostine Amikacin Amiloride Aminacrine Amination Amine Oxidase (Copper-Containing) Amines ...
  • Amidophosphoribosyltransferase (ATase), also known as glutamine phosphoribosylpyrophosphate amidotransferase (GPAT), is an enzyme responsible for catalyzing the conversion of 5-phosphoribosyl-1-pyrophosphate (PRPP) into 5-phosphoribosyl-1-amine (PRA), using the amine group from a glutamine side-chain. (wikipedia.org)