Browse
Submit Data
Databases
API
Help

Dataset Information

0 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

The activities and kinetic properties of purine phosphoribosyltransferases in developing mouse liver.

ABSTRACT: 1. The total activity of adenine phosphoribosyltransferase/liver of mice remained constant from 1 to 16 days after birth despite a fourfold increase in liver weight. The total activity of this enzyme increased fivefold from 16 to 36 days and then remained relatively constant at least until 96 days after birth. Total hypoxanthine-phosphoribosyltransferase activity/liver steadily increased between 1 and 57 days after birth. 2. The mean K(m) of 5-phosphoribosyl pyrophosphate with adenine phosphoribosyltransferase was 10.1mum between 3 and 11 days, at 64 days and at 96 days after birth. Between 17 and 51 days the mean K(m) value was 3.0mum. The K(m) of 5-phosphoribosyl pyrophosphate with hypoxanthine phosphoribosyltransferase remained constant at 28.2mum between 2 and 64 days. 3. Adenine-phosphoribosyltransferase activity was stimulated between 15 and 83% by 60mum-ATP when extracts were made between 3 and 11 days, at 64 days or at 96 days after birth. Between 17 and 51 days ATP had little stimulatory effect on the activity of this enzyme. 4. AMP competed with 5-phosphoribosyl pyrophosphate in the reaction catalysed by adenine phosphoribosyltransferase. Liver extracts containing enzyme with a low value of K(m) for 5-phosphoribosyl pyrophosphate (3mum) had a K(m)/K(i) ratio approximately half that of extracts with a high value of K(m) (10mum). 5. The results indicate that two different forms of adenine phosphoribosyltransferase can exist in mouse liver at different stages of development. The physiological significance of these findings is discussed.

SUBMITTER: Murray AW

PROVIDER: S-EPMC1270636 | biostudies-other | 1967 Aug

REPOSITORIES: biostudies-other

ACCESS DATA

Json Xml

Similar Datasets

Artemia purine phosphoribosyltransferases. Purification and characterization.

Project description:Adenine phosphoribosyltransferase (APRTase) and hypoxanthine-guanine phosphoribosyltransferase (HGPRTase) have been purified from Artemia cysts and nauplii to apparent homogeneity, as determined by SDS-PAGE. The purification includes affinity chromatography on AMP-Sepharose, which binds both enzymes, and they are eluted at different 5-phospho-alpha-D-ribosyl diphosphate (PP-Rib-P) concentrations. The purified enzymes from Artemia cysts were similar to nauplii enzymes with respect to Mr in denaturing gel electrophoresis and gel filtration, pH and cation dependence and kinetic constants for substrates and inhibitors. By Sephadex G-100 filtration, the native Mr of the adenine and hypoxanthine-guanine enzymes was estimated to be Mr 28,000 and 66,000, respectively. Analysis by SDS-PAGE revealed that the APRTase was a dimer of Mr 15,000 sub-units and the HGPRTase, a tetramer of four identical Mr 19,000 sub-units. The pH profile of the HGPRTase shows two apparent buffer-independent pH optima, at 7.0 and 9.5, while the APRTase has just one, at about pH 8-9. The purine phosphoribosyltransferase activity with adenine was highest, about tenfold the HGPRTase activity with hypoxanthine and fivefold that with guanine. Both enzymes exhibited similar requirements for divalent cations, either Mg2+, Mn2+ or Zn2+, while Ca2+ is highly inhibitory. The Km values of APRTase for adenine and PP-Rib-P are 2 and 30 microM, respectively, and the Km values of HGPRTase for hypoxanthine, guanine and PP-Rib-P are less than 1, less than 1 and 15 microM, respectively. Plots of the reciprocal enzyme activities versus reciprocal concentrations of one substrate at several fixed levels of the second one yield a pattern of inhibition by guanine and hypoxanthine. Product-inhibition studies indicated that AMP is a competitive inhibitor with respect to PP-Rib-P in the APRTase reaction, while the HGPRTase shows a mixed inhibition by GMP.

| S-EPMC1150056 | biostudies-other

Inhibition of purine phosphoribosyltransferases from Ehrlich ascites-tumour cells by purine nucleotides.

Project description:1. The purine bases adenine, hypoxanthine and guanine were rapidly incorporated into the nucleotide fraction of Ehrlich ascites-tumour cells in vivo. 2. The reaction of 5'-phosphoribosyl pyrophosphate with adenine phosphoribosyltransferase from ascites-tumour cells (K(m) 6.5-11.9mum) was competitively inhibited by AMP, ADP, ATP and GMP (K(i) 7.5, 21.9, 395 and 118mum respectively). Similarly the reactions of 5'-phosphoribosyl pyrophosphate with both hypoxanthine phosphoribosyltransferase and guanine phosphoribosyltransferase (K(m) 18.4-31 and 37.6-44.2mum respectively) were competitively inhibited by IMP (K(i) 52 and 63.5mum) and by GMP (K(i) 36.5 and 5.9mum). 3. The nucleotides tested as inhibitors did not appreciably compete with the purine bases in the phosphoribosyltransferase reactions. 4. It was postulated that the purine phosphoribosyltransferases of Ehrlich ascites-tumour cells may be effectively separated from the adenine nucleotide pool of these cells.

| S-EPMC1265200 | biostudies-other

Kinetic Characterization and Inhibition of <i>Trypanosoma cruzi</i> Hypoxanthine-Guanine Phosphoribosyltransferases.

Project description:Chagas disease, caused by the parasitic protozoan Trypanosoma cruzi, affects over 8 million people worldwide. Current antiparasitic treatments for Chagas disease are ineffective in treating advanced, chronic stages of the disease, and are noted for their toxicity. Like most parasitic protozoa, T. cruzi is unable to synthesize purines de novo, and relies on the salvage of preformed purines from the host. Hypoxanthine-guanine phosphoribosyltransferases (HGPRTs) are enzymes that are critical for the salvage of preformed purines, catalyzing the formation of inosine monophosphate (IMP) and guanosine monophosphate (GMP) from the nucleobases hypoxanthine and guanine, respectively. Due to the central role of HGPRTs in purine salvage, these enzymes are promising targets for the development of new treatment methods for Chagas disease. In this study, we characterized two gene products in the T. cruzi CL Brener strain that encodes enzymes with functionally identical HGPRT activities in vitro: TcA (TcCLB.509693.70) and TcC (TcCLB.506457.30). The TcC isozyme was kinetically characterized to reveal mechanistic details on catalysis, including identification of the rate-limiting step(s) of catalysis. Furthermore, we identified and characterized inhibitors of T. cruzi HGPRTs originally developed as transition-state analogue inhibitors (TSAIs) of Plasmodium falciparum hypoxanthine-guanine-xanthine phosphoribosyltransferase (PfHGXPRT), where the most potent compound bound to T. cruzi HGPRT with low nanomolar affinity. Our results validated the repurposing of TSAIs to serve as selective inhibitors for orthologous molecular targets, where primary and secondary structures as well as putatively common chemical mechanisms are conserved.

| S-EPMC9536471 | biostudies-literature

Developmental changes in purine phosphoribosyltransferases in human and rat tissues.

Project description:1. The hypoxanthine/guanine and adenine phosphoribosyltransferase activities in a wide variety of human tissues were studied during their growth and development from foetal life onward. A wide range of activities develop after birth, with especially high values in the central nervous system and testes. 2. Postnatal development of hypoxanthine/guanine phosphoribosyltransferase was also defined in the rat. Although there were increases in the central nervous system and testes, there was also a rise in activity in the liver, which was less marked in man. 3. A sensitive radiochemical assay method, using dTTP to inhibit 5'-nucleotidase activity, suitable for tissue extracts, was developed. 4. No definite evidence of the existence of tissue-specific isoenzymes of hypoxanthine/guanine or adenine phosphoribosyltransferase was found. Hypoxanthine/guanine phosphoribosyltransferase in testes, however, had a significantly different thermal-denaturation rate constant. 5. The findings are discussed in an attempt to relate activity of hypoxanthine/guanine phosphoribosyltransferase to biological function. Growth as well as some developmental changes appear to be related to increase in the activity of this enzyme.

| S-EPMC1164271 | biostudies-other

Genome-wide kinetic properties of transcriptional bursting in mouse embryonic stem cells

Project description:This SuperSeries is composed of the SubSeries listed below.

2020-06-04 | GSE132593 | GEO

Genome-wide kinetic properties of transcriptional bursting in mouse embryonic stem cells.

Project description:Transcriptional bursting is the stochastic activation and inactivation of promoters, contributing to cell-to-cell heterogeneity in gene expression. However, the mechanism underlying the regulation of transcriptional bursting kinetics (burst size and frequency) in mammalian cells remains elusive. In this study, we performed single-cell RNA sequencing to analyze the intrinsic noise and mRNA levels for elucidating the transcriptional bursting kinetics in mouse embryonic stem cells. Informatics analyses and functional assays revealed that transcriptional bursting kinetics was regulated by a combination of promoter- and gene body-binding proteins, including the polycomb repressive complex 2 and transcription elongation factors. Furthermore, large-scale CRISPR-Cas9-based screening identified that the Akt/MAPK signaling pathway regulated bursting kinetics by modulating transcription elongation efficiency. These results uncovered the key molecular mechanisms underlying transcriptional bursting and cell-to-cell gene expression noise in mammalian cells.

| S-EPMC7299619 | biostudies-literature

Purine-phosphoribosyltransferase activities in rat and mouse tissues and in Ehrlich ascites-tumour cells.

Project description:1. The activities of adenine phosphoribosyltransferase and hypoxanthine phosphoribosyltransferase in extracts of rat and mouse liver, brain, spleen, heart and kidney, of rat bone marrow and of Ehrlich ascites-tumour cells have been measured. The specific activity of adenine phosphoribosyltransferase in tumour cells (3mmu-moles of nucleotide formed/min./mg. of protein) was between 15 and 60 times the activity of any mouse tissue examined. Hypoxanthine-phosphoribosyltransferase activity was greater in extracts of tumour cells than in mouse tissues, but the difference was not great. 2. The specific activities of both adenine phosphoribosyltransferase and hypoxanthine phosphoribosyltransferase in ascites-tumour cells decreased respectively by 57% and 36% 2 days after the cells had been inoculated into mice. After 4 days of tumour growth the specific activities of both enzymes increased, reaching a maximum at 10 days. 3. The activity of adenine phosphoribosyltransferase in rat-liver extracts increased steadily up to 4 days after partial hepatectomy, and was still above the control value after 14 days. Hypoxanthine-phosphoribosyltransferase activity in extracts of regenerating rat liver did not increase until the second day after operation and had begun to decrease by the fourth day. 4. From the results it was concluded that adenine phosphoribosyltransferase and hypoxanthine phosphoribosyltransferase may be physiologically important enzymes in rapidly growing tissues, and that inhibitors of the former enzyme have potential value in chemotherapy.

| S-EPMC1265199 | biostudies-other

Changes in ornithine decarboxylase and antizyme activities in developing mouse brain.

Project description:A macromolecular inhibitor to ornithine decarboxylase (ODC) present in mouse brain was identified as ODC antizyme [Fong, Heller & Canellakis (1976) Biochim. Biophys. Acta 428, 456-465; Heller, Fong & Canellakis (1976) Proc. Natl. Acad. Sci. U.S.A. 73, 1858-1862] on the basis of kinetic properties, Mr and reversal of its inhibition by antizyme inhibitor. The brain antizyme, however, did not cross-react immunochemically with any of seven monoclonal antibodies to rat liver antizyme. ODC activity in mouse brain rapidly decreased after birth, in parallel with putrescine content, and almost disappeared by 3 weeks of age. Free antizyme activity appeared shortly after birth and increased gradually, whereas ODC-antizyme complex already existed at birth and then gradually decreased. Thus total amount of antizyme remained about the same throughout the developmental period in mouse brain. In addition to ODC-antizyme complex, inactive ODC protein was detected by radioimmunoassay in about the same level as the complex at 3 weeks of age. Upon cycloheximide treatment, both free ODC activity and ODC-antizyme complex rapidly disappeared, although free antizyme and the inactive ODC protein were both quite stable.

| S-EPMC1148926 | biostudies-other

A time-resolved multi-omic atlas of the developing mouse liver.

Project description:Liver organogenesis and development are composed of a series of complex, well-orchestrated events. Identifying key factors and pathways governing liver development will help elucidate the physiological and pathological processes including those of cancer. We conducted multidimensional omics measurements including protein, mRNA, and transcription factor (TF) DNA-binding activity for mouse liver tissues collected from embryonic day 12.5 (E12.5) to postnatal week 8 (W8), encompassing major developmental stages. These data sets reveal dynamic changes of core liver functions and canonical signaling pathways governing development at both mRNA and protein levels. The TF DNA-binding activity data set highlights the importance of TF activity in early embryonic development. A comparison between mouse liver development and human hepatocellular carcinoma (HCC) proteomic profiles reveal that more aggressive tumors are characterized with the activation of early embryonic development pathways, whereas less aggressive ones maintain liver function-related pathways that are elevated in the mature liver. This work offers a panoramic view of mouse liver development and provides a rich resource to explore in-depth functional characterization.

| S-EPMC7050524 | biostudies-literature

Some properties of galactokinase in developing rat liver.

Project description:1. The nature of the galactokinase present in the livers of foetal, newborn and adult rats was examined by the application of several separation procedures and by measurement of a range of kinetic parameters. 2. No evidence of enzyme heterogeneity at any stage of development was found during gel filtration on Sephadex G-100, column chromatography on DEAE-cellulose or a variety of electrophoretic procedures. 3. The K(m) values, inhibition characteristics and other kinetic parameters appear to remain constant during development. 4. Rat liver galactokinase activity does not adapt to dietary changes in either the adult or the newborn rat; hence it is unlikely that the presence of galactose in milk controls the enzymic activity profile during development. 5. On the present evidence it is concluded that only one form of galactokinase is present in rat liver and that the enzymic activity is controlled by non-dietary factors.

| S-EPMC1198790 | biostudies-other

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

Tweets

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data