Nucleotide metabolism by microsomal UDP-glucuronyltransferase and nucleoside diphosphatase as determine by 31P nuclear-magnetic-resonance spectroscopy.
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ABSTRACT:
SUBMITTER: Finch SA
PROVIDER: S-EPMC1186459 | biostudies-other | 1979 Mar
REPOSITORIES: biostudies-other
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Project description:PurposePhosphorus magnetic resonance spectroscopy ((31)P-MRS) affords unique insight into cardiac energetics but has a low intrinsic signal-to-noise ratio (SNR) in humans. Theory predicts an increased (31)P-MRS SNR at 7T, offering exciting possibilities to better investigate cardiac metabolism. We therefore compare the performance of human cardiac (31)P-MRS at 7T to 3T, and measure T1s for (31)P metabolites at 7T.MethodsMatched (31)P-MRS data were acquired at 3T and 7T, on nine normal volunteers. A novel Look-Locker CSI acquisition and fitting approach was used to measure T1s on six normal volunteers.ResultsT1s in the heart at 7T were: phosphocreatine (PCr) 3.05 ± 0.41s, γ-ATP 1.82 ± 0.09s, α-ATP 1.39 ± 0.09s, β-ATP 1.02 ± 0.17s and 2,3-DPG (2,3-diphosphoglycerate) 3.05 ± 0.41s (N = 6). In the field comparison (N = 9), PCr SNR increased 2.8× at 7T relative to 3T, the Cramer-Ráo uncertainty (CRLB) in PCr concentration decreased 2.4×, the mean CRLB in PCr/ATP decreased 2.7× and the PCr/ATP SD decreased 2×.ConclusionCardiac (31)P-MRS at 7T has higher SNR and the spectra can be quantified more precisely than at 3T. Cardiac (31)P T1s are shorter at 7T than at 3T. We predict that 7T will become the field strength of choice for cardiac (31)P-MRS.
| S-EPMC4106879 | biostudies-literature
Project description:We identified SA1684 as a Staphylococcus aureus virulence gene using a silkworm infection model. The SA1684 gene product carried the DUF402 domain, which is found in RNA-binding proteins, and had amino acid sequence similarity with a nucleoside diphosphatase, Streptomyces coelicolor SC4828 protein. The SA1684-deletion mutant exhibited drastically decreased virulence, in which the LD50 against silkworms was more than 10 times that of the parent strain. The SA1684-deletion mutant also exhibited decreased exotoxin production and colony-spreading ability. Purified SA1684 protein had Mn(2+)- or Co(2+)-dependent hydrolyzing activity against nucleoside diphosphates. Alanine substitutions of Tyr-88, Asp-106, and Asp-123/Glu-124, which are conserved between SA1684 and SC4828, diminished the nucleoside diphosphatase activity. Introduction of the wild-type SA1684 gene restored the hemolysin production of the SA1684-deletion mutant, whereas none of the alanine-substituted SA1684 mutant genes restored the hemolysin production. RNA sequence analysis revealed that SA1684 is required for the expression of the virulence regulatory genes agr, sarZ, and sarX, as well as metabolic genes involved in glycolysis and fermentation pathways. These findings suggest that the novel nucleoside diphosphatase SA1684 links metabolic pathways and virulence gene expression and plays an important role in S. aureus virulence.
| S-EPMC5009239 | biostudies-literature
Project description:We sought to examine, via Phosphorus-31 magnetic resonance spectroscopy ((31)P-MRS) in a case-control design, whether bioenergetic deficits in autism spectrum disorders extend to the brain and muscle. Six cases with autism spectrum disorder with suspected mitochondrial dysfunction (age 6-18 years) and 6 age/sex-matched controls underwent (31)P magnetic resonance spectroscopy. The outcomes of focus were muscle resting phosphocreatine and intracellular pH as well as postexercise phosphocreatine recovery time constant and frontal brain phosphocreatine. Intracellular muscle pH was lower in each autism spectrum disorder case than their matched control (6/6, P = .03; P = .0048, paired t test). Muscle phosphocreatine (5/6), brain phosphocreatine (3/4), and muscle phosphocreatine recovery time constant (3/3) trends were in the predicted direction (not all participants completed each). This study introduces (31)P magnetic resonance spectroscopy as a noninvasive tool for assessment of mitochondrial function in autism spectrum disorder enabling bioenergetic assessment in brain and provides preliminary evidence suggesting that bioenergetic defects in cases with autism spectrum disorder are present in muscle and may extend to brain.
| S-EPMC3931549 | biostudies-literature
Project description:Abnormal cell membrane metabolism is associated with many neuropsychiatric disorders. Free phosphomonoesters and phosphodiesters, which can be detected by in vivo 31P magnetic resonance spectroscopy (MRS), are important cell membrane building blocks. However, the quantification of phosphoesters has been highly controversial even in healthy individuals due to overlapping signals from macromolecule membrane phospholipids (MP). In this study, high signal-to-noise ratio (SNR) cerebral 31P MRS spectra were acquired from healthy volunteers at both 3 and 7 Tesla. Our results indicated that, with minimal spectral interference from MP, the [phosphocreatine (PCr)]/[phosphocholine (PC) + glycerophosphocholine (GPC)] ratio measured at 7 Tesla agreed with its value expected from biochemical constraints. In contrast, the 3 Tesla [PCr]/[PC+GPC] ratio obtained using standard spectral fitting procedures was markedly smaller than the 7 Tesla ratio and than the expected value. The analysis suggests that the commonly used spectral model for MP may fail to capture its complex spectral features at 3 Tesla, and that additional prior knowledge is necessary to reliably quantify the phosphoester signals at low magnetic field strengths when spectral overlapping is significant.
| S-EPMC7971532 | biostudies-literature
Project description:Rabbit liver UDP-glucuronyltransferase activity was resolved into two separate fractions on DEAE-cellulose, one containing most of the transferase activity toward oestrone and the other most of the activity toward p-nitrophenol. These two activities were completely separated by rechromatography of each fraction on a second DEAE-cellulose column.
| S-EPMC1184011 | biostudies-other
Project description:Hepatic UDP-glucuronyltransferase activity was resolved into two fractions, one exhibiting oestrone glucuronyltransferase activity and the other exhibiting p-nitrophenol glucuronyltransferase activity. Hydroxyapatite-column chromatography removed greater than 95% of the phospholipids from both preparations. The partially purified delipidated enzymes were essentially devoid of catalytic activity, but activities were restored by the addition of phospholipids or phosphatidylcholine mixtures containing various saturated and unsaturated fatty acids. Both oestrone and p-nitrophenol glucuronyl-transferase activities were reconstituted to similar degrees with the phosphatidylcholine mixtures. When purified phospholipids were tested, phosphatidylcholine and lysophosphatidylcholine were most effective in restoring activity, whereas phosphatidylethanolamine was the least effective. These results further suggest that oestrone and p-nitrophenol UDP-glucuronyltransferases are dependent on phospholipids for their activity.
| S-EPMC1186595 | biostudies-other
Project description:We have demonstrated that acylphosphatase possesses ATP-diphosphohydrolase (apyrase-like) activity. In fact, acylphosphatase first catalyses the hydrolysis of the gamma-phosphate group of nucleoside triphosphates, and then attacks the beta-phosphate group of the initially produced nucleoside diphosphates, generating nucleoside monophosphates. In contrast, it binds nucleoside monophosphates but does not catalyse their hydrolyses. The calculated k(cat) values for the nucleoside triphosphatase activity of acylphosphatase are of the same order of magnitude as those displayed by certain G-proteins. An acidic environment enhances the apyrase-like activity of acylphosphatase. The true nucleotide substrates of acylphosphatase are free nucleoside di- and triphosphates, as indicated by the Mg(2+) ion inhibition of the activity. We have also demonstrated that, although nucleoside triphosphates are still hydrolysed at pH 7.2 and 37 degrees C, in the presence of millimolar Mg(2+) concentrations this occurs at a lower rate. Taken together with the previously observed strong increase of acylphosphatase levels during induced cell differentiation, our findings suggest that acylphosphatase plays an active role in the differentiation process (as well as in other processes, such as apoptosis) by modulating the ratio between the cellular levels of nucleoside diphosphates and nucleoside triphosphates.
| S-EPMC1221118 | biostudies-other
Project description:Highly purified bilirubin UDP-glucuronyltransferase from Wistar-rat liver, when reconstituted with Gunn-rat liver microsomes (microsomal fraction), was able to catalyse the conversion of unesterified bilirubin into both bilirubin monoglucuronide and diglucuronide. Under zero-order kinetic conditions for monoglucuronide formation, the fraction of bilirubin diglucuronide formed by incubation of bilirubin with the reconstituted highly purified transferase accounted for 18% of total bilirubin glucuronides, which was only slightly lower than the fraction of diglucuronides (23% of total bilirubin glucuronides) formed by incubation with hepatic microsomes in the presence of UDP-N-acetylglucosamine or Lubrol. The reconstituted purified enzyme also catalysed the UDP-glucuronic acid-dependent conversion of bilirubin monoglucuronide into diglucuronide and, when bilirubin was incubated with UDP-glucose or UDP-xylose, the formation of bilirubin glucosides and xylosides respectively. These results suggest that a single microsomal bilirubin UDP-glycosyltransferase may be responsible for the formation of bilirubin mono- and di-glycosides.
| S-EPMC1144319 | biostudies-other
Project description:The gene for a Nudix enzyme (SP_1669) was found to code for a UDP-X diphosphatase. The SP_1669 gene is localized among genes encoding proteins that participate in cell division in Streptococcus pneumoniae. One of these genes, MurF, encodes an enzyme that catalyzes the last step of the Mur pathway of peptidoglycan biosynthesis. Mur pathway substrates are all derived from UDP-glucosamine and all are potential Nudix substrates. We showed that UDP-X diphosphatase can hydrolyze the Mur pathway substrates UDP-N-acetylmuramic acid and UDP-N-acetylmuramoyl-L-alanine. The 1.39 Å resolution crystal structure of this enzyme shows that it folds as an asymmetric homodimer with two distinct active sites, each containing elements of the conserved Nudix box sequence. In addition to its Nudix catalytic activity, the enzyme has a 3'5' RNA exonuclease activity. We propose that the structural asymmetry in UDP-X diphosphatase facilitates the recognition of these two distinct classes of substrates, Nudix substrates and RNA. UDP-X diphosphatase is a prototype of a new family of Nudix enzymes with unique structural characteristics: two monomers, each consisting of an N-terminal helix bundle domain and a C-terminal Nudix domain, form an asymmetric dimer with two distinct active sites. These enzymes function to hydrolyze bacterial cell wall precursors and degrade RNA.
| S-EPMC3655063 | biostudies-literature
Project description:BACKGROUND:Brain energy metabolism is critical for supporting synaptic function and information processing. A growing body of evidence suggests abnormalities in brain bioenergetics in psychiatric disorders, including both bipolar disorder (BD) and schizophrenia. 31P magnetic resonance spectroscopy provides a noninvasive window into these processes in vivo. Using this approach, we previously showed that patients with BD show normal adenosine triphosphate (ATP) and phosphocreatine levels at rest but cannot maintain normal ATP levels in the visual cortex during times of high energy demand (photic stimulation). Because ATP is replenished from phosphocreatine via the creatine kinase reaction, we have now measured the creatine kinase forward reaction rate constant in BD. METHODS:We studied 20 patients experiencing a first episode of BD and 28 healthy control participants at 4T and quantified creatine kinase forward reaction rate constant using 31P magnetization transfer magnetic resonance spectroscopy as described previously. RESULTS:We found a significant reduction in creatine kinase forward reaction rate constant in the BD group (F = 4.692, p = .036), whereas brain ATP and phosphocreatine concentrations, as well as brain parenchymal pH, were normal. CONCLUSIONS:These results pinpoint a specific molecular mechanism underlying our previous observation of an inability to replenish brain ATP during times of high energy demand in BD.
| S-EPMC5632123 | biostudies-literature