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Query: EC:2.4.2.7 (adenine phosphoribosyltransferase)
 692 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The mechanism of ATP biosynthesis from adenine was studied on the cell-free extract of Corynebacterium species that produces ATP from exogenous adenine, using labeled substrates. As a source of the ribosyl component of the ATP molecule, phosphoribosyl pyrophosphate (PRPP) and ribose-5-phosphate (P5P) were tested. The experiments with PRPP showed adenine phosphoribosyl transferase (EC 2.4.2.7) activity in the extract responsible for the AMP formation from PRPP and adenine. The minimal reaction mixture based on R5P was found to include only magnesium ions, in addition to R5P, adenine, and the extract. This mixture provided the synthesis of not only C14-AMP but also C14-ADP and C14-ATP from C14-adenine. Phosphorylation of C14-AMP to yield C14-ATP was related to the presence of R5P in the mixture. The synthesis of C14-ATP from C14-adenine also took place when R5W was substituted for glucose in the minima mixture.
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PMID:[The mechanism of adenine nucleotide biosynthesis from adenine in Corynebacterium species]. 9 86

Hypoxanthine phosphoribosyltransferase (EC 2.4.2.8) from rat brain or human erytherocytes can be irreversibly inactivated by incubation with periodate-oxidized analogues of the enzyme products GMP or IMP. This inhibition is specific and directed against the product binding site of the enzyme. Inactivation is not produced by periodate-oxidized AMP or other aldehydes, for example periodate-oxidized glycerol. The inactivation is concomitant with the binding of the inhibitor to the enzyme protein. The bound inhibitor cannot be removed from the protein by dialysis, Sephadex chromatography or polyacrylamide-gel electrophoresis. Adenine phosphoribosyltransferase (EC 2.4.2.7), on the other hand, is not influenced by any of the inhibitors mentioned above.
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PMID:Irreversible inactivation of hypoxanthine phosphoribosyltransferase by periodate oxidized nucleotides. 16 42

A model is proposed for the partial depletion of the adenine nucleotide pool in the ischemic perfused rat heart which involves seven enzymes: adenylate cyclase, 3',5'-cyclic AMP phosphodiesterase, 5'-nucleotidase, adenosine kinase, adenosine deaminase, purine nucleoside phosphorylase, and inorganic pyrophosphatase. The computer implementation of this model is in terms of rate laws, several of which were obtained by a systematic least-squares fitting procedure. Depletion of the adenine nucleotide pool is initiated by the release of endogenous noradrenaline into the interstitial fluid, which results from a fall in tissue PO2, and the subsequent activation of adenylate cyclase. In this model the substrate for 5'-nucleotidase is a membrane-bound AMP pool formed by hydrolysis of extracellular fluid and functions as a vasodilator; excess adenosine is incorporated into the tissue by a "permease" with Michaelis-Menten kinetics and converted to AMP, inosine, and hypoxanthine. Alternative mechanisms, such as the deamination of AMP by adenylate deaminase and conversion of AMP to adenine by AMP pyrophosphorylase, were rejected primarily on qualitative biochemical grounds.
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PMID:Computer simulation of ischemic rat heart purine metabolism. I. Model construction. 19 89

The adenine phosphoribosyltransferase (AMP: pyrophosphate phosphoribosyltransferase, EC 2.4.2.7) of rat liver was purified to a specific activity of 1.1 mumol of AMP formed per min per mg. The enzyme activity is associated with an apparently homogenous protein as shown by isoelectrofocusing, acrylamide gel electrophoresis, and N-terminal amino acids analysis (phenylalanine). The molecular weight of the enzyme was estimated to be approx. 20 000 by acrylamide gel electrophoresis in the presence of sodium dodecylsulfate and by sucrose density gradient zone sedimentation. The rat liver enzyme exhibited initial burst synthesis of AMP when 1-pyrophosphorylribose 5-phosphate was added. The 1-pyrophosphorylribose 5-phosphate initial-burst activity copurifies with the adenine phosphoribosyltransferase activity. A PH optimum of 10.0 was demonstrable for the adenine phosphoribosyltransferase. The initial-burst and steady-state phases of AMP synthesis catalyzed by highly purified rat liver adenine phosphoribosyltransferase have been partially characterized by the use of ligands which bind to sulfhydryl groups. Studies utilizing p-chloromercuribenzoate and HgCl2 as inhibitors of AMP sulfhydryl during the initial-burst and steady-state phases have revealed that sulfhydryl groups with different rates of ligand binding are present in the enzyme. The initial-burst phase was thereby delineated from the steady-state phase by use of these mercurial ligands. This delineation was also accomplished by titration with the Mg-2+ chelator, EDTA. The inhibitory effects of mercurials and EDTA were reversed by beta-mercaptoethanol and excess Mg-2+, respectively. Quantitative binding studies with 5,5'-dithiobis(2-nitrobenzoic acid) and p-chloromercuribenzoate yielded values of 3.65 and 3.6 mol of sulfhydryl per mol of enzyme, respectively. 3.3 mol of cysteic acid per mol of performic acid-oxidized enzyme were found by amino acid analysis.
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PMID:Purification and properties of rat liver adenine phosphoribosyltransferase. 23 79

In this report, we demonstrate the feasibility of transforming mouse cells deficient in adenine phosphoribosyltransferase (aprt; AMP:pyrophosphate phosphoribosyltransferase, EC 2.4.2.7) to the aprt+ phenotype by means of DNA-mediated gene transfer. Transformation was effected by using unfractionated high molecular weight genomic DNA from Chinese hamster, human, and mouse cells and restriction endonuclease-digested DNA from rabbit liver. The transformation frequency observed was between 1 and 10 colonies per 10(6) cells per 20 microgram of donor DNA. Transformants displayed enzymatic activity that was donor derived as demonstrated by isoelectric focusing of cytoplasmic extracts. These transformants fall into two classes: those that are phenotypically stable when grown in the absence of selective pressure and those that are phenotypically unstable under the same conditions.
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PMID:DNA-mediated transfer of the adenine phosphoribosyltransferase locus into mammalian cells. 28 19

Adenine aminohydrolase (EC 3.5.4.2) from four species of Leishmania and from Crithidia fasciculata was examined for specific activities, affinity for substrate (adenine), and stability to heat. All were found to be strongly and non-competitively inhibited by both coformycin and deoxycoformycin, two tight-binding inhibitors of adenosine deaminase (adenosine aminohydrolase, EC 3.5.4.4). Deoxycoformycin is the more potent inhibitor of the two. Neither inhibitor was active against the purine phosphoribosyltransferases. When deoxycoformycin was added to the defined growth medium containing hypoxanthine as the purine source, the growth of C. fasciculata was unaffected, but when adenine was the purine source for the organism, severe inhibition resulted. This implies that hypoxanthine is the obligatory base for nucleotide synthesis and that the adenine phosphoribosyltransferase (AMP:pyrophosphate phosphoribosyltransferase, EC 2.4.2.7) is, in some manner,idenied access to exogenous substrate.
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PMID:Adenine aminohydrolase: occurrence and possible significance in trypanosomid flagellates. 29 Oct 31

Independently obtained mutations (apt) of resistance to DAP (2,6-diaminopurine) and MP (6-methylpurine), that affect adenine phosphoribosyltransferase (APRT) in Escherichia coli, are different in their effect on the conversion of several substrates of APRT, such as DAP, MP, MAP (6-methylaminopurine) and adenine, to their nucleotide derivatives. Most of mutants were resistant to DAP and MP, unable to utilize MAP (as purine source) and differed in their ability to uptake adenine from the medium. Among the mutants capable to utilize adenine the following types are found: (1) resistant to DAP and MP, but capable of utilizing MAP, and (2) resistant to DAP, capable of utilizing MAP, but sensitive to MP. The gene apt encoding APRT is located between genes proC and purE; the frequency of cotransduction between proC and several apt mutations is found to be 1.7--2% and purE-apt--to be 5--10.8%. Mutations apt block up the ability of purine-dependent (pur) bacteria lacking purine nucleoside phosphorylase (pup) to use purine ribonucleosides as purine sources. The degree of that blocking depends on the ability of apt mutants to convert adenine to AMP via APRT. These observations confirm our previous data, that the ability of pur pup mutants to use purine ribonucleosides depends on the activity of APRT.
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PMID:[Mutations of resistance to 2,6-diaminopurine and 6-methylpurine that affect adenine phosphoribosyltransferase in Escherichia coli K-12]. 34 74

The adenine analog 4-aminopyrazolo(3,4-d)pyrimidine inhibits the growth of the kinetoplastid (trypanosomatid) flagellate Crithidia fasciculata. This inhibition is partially overcome only by adenine (of a number of purines tested), with an inhibition index of 0.025. More effective reversal of inhibition is obtained with any of a number of naturally occurring pyrimidine compounds, up to a concentration of 0.18 mM. Higher concentrations of pyrimidines or addition of guanine, as well as adenine and uracil, to the medium increases inhibition. The analog (presumably as the ribonucleotide) was found not to be inhibitory to any enzyme of the pyrimidine biosynthetic pathway that could be tested. It is suggested that the analog competes with adenine for adenine phosphoribosyltransferase (AMP:pyrophosphate phosphoribosyltransferase, EC 2.4.2.7), is converted to a ribonucleotide, and is incorporated into nucleic acid.
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PMID:Inhibitory action of the adenine analog, 4-aminopyrazolo(3,4-d)pyrimidine, in Crithidia fasciculata. 55 73

Changes in hepatic purine enzyme activities of chicks fed diets containing 11%, 20%, 43% and 80% protein were correlated with protein intake and uric acid production in order to identify those enzymes with activities that parallel closely and may regulate uric acid production. Nucleoside phosphorylase, xanthine dehydrogenase, adenylosuccinate synthetase and adenosine kinase correlated positively with protein intake and uric acid production. Adenosine deaminase, 5'-nucleotidase (AMP), adenylate deaminase and adenine phosphoribosyltransferase correlated negatively with protein intake and uric acid production. Hypoxanthine phosphoribosyltransferase and 5'-nucleotidase (IMP) were unaffected by protein intake and did not correlate with uric acid production. The ratio of adenosine kinase to adenosine deaminase correlated positively with protein intake and uric acid production. The increased activities of adenylosuccinate synthetase and adenosine kinase, along with the reduced activities of 5'-nucleotidase and adenylate deaminase, in liver from chickens fed the 80% compared with the 11% protein diet demonstrate enhanced synthesis of adenine nucleotides. Since adenine nucleotides are essential cofactors for de novo purine synthesis, it is proposed that adenylosuccinate synthetase, adenosine kinase, 5'-nucleotidase and adenylate deaminase are key enzymes involved in the regulation of purine biosynthesis.
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PMID:Protein intake, hepatic purine enzyme levels and uric acid production in growing chicks. 61 42

The purine salvage pathway enzyme adenine phosphoribosyltransferase (AMP: pyrophosphate phosphoribosyltransferase EC 2.42.7) has been purified to greater than 85% homogeneity from crude rat liver 100,000 x g supernatant in one step by affinity chromatography. The enzyme binds to an AMP-agarose column and is eluted off the column by 1 mM 5-phosphoribosyl pyrophosphate with a 50 to 80% recovery. Enzyme kinetics indicate that the mechanism of the specific elution is due to competition of the product AMP and substrate 5-phosphoribosyl pyrophosphate for the same site on the enzyme.
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PMID:Purification of adenine phosphoribosyltransferase by affinity chromatography. 74 18


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