Abstract：
:The various interactions of rat liver dihydrofolate reductase with two unconjugated 7,8-dihydropteridines, 7,8-dihydrobiopterin and 6-methyl-7,8-dihydropteridine, have been compared with those of 7,8-dihydrofolate and folate. Of particular interest was the reactivity demonstrated by 7,8-dihydrobiopterin because of the potential physiological significance of this reaction both in the regeneration of tetrahydrobiopterin, a cofactor for various biological hydroxylations, and as a step in the biosynthesis of this compound from GTP. Kinetic experiments gave Km values of 0.17, 6.42, and 10.2 microM for 7,8-dihydrofolate, 7,8-dihydrobiopterin, and 6-methyl-7,8-dihydropteridine, respectively, with Vmax = 6.22, 2.39, and 1.54 mumol min-1 mg-1. With folate the enzyme showed high affinity (Km = 0.88 microM) but low Vmax (0.20 mumol min-1 mg-1). The natural cofactor was NADPH and a Km of approximately 0.7 microM was measured with each substrate. The enzyme was activated by both p-hydroxymercuribenzoate and urea when assayed with 7,8-dihydrofolate but was inhibited when 7,8-dihydrobiopterin was the substrate. The pH optimum for dihydrofolate reduction was 4 with enhancement at pH greater than or equal to 5.5 in the presence of 1 M NaCl. Peak activity with 7,8-dihydrobiopterin occurred at pH 4.8; this was shifted to pH 5.3 but was not enhanced by 1 M NaCl. Inhibition with methotrexate was similar whether the enzyme was assayed with either the conjugated or unconjugated 7,8-dihydro derivatives. The rat liver enzyme, highly unstable after purification, was stabilized in the presence of the nonionic detergent, Tween-20 (0.1%); however, the comparative properties toward the conjugated and unconjugated substrates were not altered by this treatment.
journal_name
Arch Biochem Biophysjournal_title
Archives of biochemistry and biophysicsauthors
Webber S,Whiteley JMdoi
10.1016/0003-9861(85)90674-5subject
Has Abstractpub_date
1985-02-01 00:00:00pages
681-90issue
2eissn
0003-9861issn
1096-0384pii
0003-9861(85)90674-5journal_volume
236pub_type
杂志文章abstract：:Thermal perturbation techniques have been used to probe structural features of the nicotinic acetylcholine receptor (AcChR). The information obtained from differential scanning calorimetry (DSC) of AcChR membranes (M.C. Farach and M. Martinez-Carrion (1983) J. Biol. Chem. 258, 4176) in the absence and in the presence ...
journal_title：Archives of biochemistry and biophysics
pub_type： 杂志文章
doi：10.1016/0003-9861(87)90319-5
更新日期：1987-10-01 00:00:00
abstract：:Calmodulin, a calcium-binding protein with no known enzymatic activity but multiple, in vitro effector activities, has been purified to apparent homogeneity from the unicellular green alga Chlamydomonas reinhardtii and compared to calmodulin from vertebrates and higher plants. Chlamydomonas calmodulin was characterize...
journal_title：Archives of biochemistry and biophysics
pub_type： 杂志文章
doi：10.1016/0003-9861(84)90127-9
更新日期：1984-02-15 00:00:00
abstract：:Secreted frizzled-related protein (sFRP)-1 is a Wnt antagonist that inhibits breast carcinoma cell motility, whereas the secreted glycoprotein thrombospondin-1 stimulates adhesion and motility of the same cells. We examined whether thrombospondin-1 and sFRP-1 interact directly or indirectly to modulate cell behavior. ...
journal_title：Archives of biochemistry and biophysics
pub_type： 杂志文章
doi：10.1016/j.abb.2011.03.004
更新日期：2011-05-15 00:00:00
abstract：:In 5-aminolevulinic acid (ALA)-based photodynamic therapy (PDT), ALA taken up by tumor cells is metabolized to protoporphyrin IX (PpIX), which sensitizes photodamage leading to apoptotic or necrotic cell death. Since lipophilic PpIX originates in mitochondria, we postulated that photoperoxidation of highly unsaturated...
journal_title：Archives of biochemistry and biophysics
pub_type： 杂志文章
doi：10.1016/j.abb.2004.09.025
更新日期：2005-01-15 00:00:00
abstract：:DNA damage has been postulated as a mechanism of neuronal death in Parkinson's disease (PD). In the present study, genomic DNA was isolated from eight brain regions (frontal, temporal, and occipital cortex, hippocampus, caudate/putamen, thalamus, cerebellum, and midbrain) from five neuropathologically confirmed cases ...
journal_title：Archives of biochemistry and biophysics
pub_type： 杂志文章
doi：10.1016/j.abb.2006.02.018
更新日期：2006-05-15 00:00:00
abstract：:After an energy source shift-down, Escherichia coli accumulates 70 S ribosome-mRNA complexes ("70 S monosomes"). The monosome mRNA strands are predominantly primary transcription products with purine nucleoside 5'-triphosphate and 5'-diphosphate termini present at a 1:2 ratio. The number-average chain length is 564 +/...
journal_title：Archives of biochemistry and biophysics
pub_type： 杂志文章
doi：10.1016/0003-9861(85)90367-4
更新日期：1985-08-15 00:00:00
abstract：:Kinetic analysis has shown that dimethylnitrosamine, dipropylnitrosamine, dibutylnitrosamine, and diphenylnitrosamine initially act as reversible competitive inhibitors with respect to the substrate, acetylthiocholine chloride. The inhibitor constants Ki vary from 21-30 microM for the aliphatic nitrosamines to 8.2 mic...
journal_title：Archives of biochemistry and biophysics
pub_type： 杂志文章
doi：10.1016/0003-9861(90)90500-x
更新日期：1990-06-01 00:00:00
abstract：:The key technique in proteome analysis is high-resolution two-dimensional (2D) electrophoretic separation of proteins from biological samples. This method combines isoelectric focusing (IEF) and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Derivatization of protein carbonyls with 2, 4-dinitrop...
journal_title：Archives of biochemistry and biophysics
pub_type： 杂志文章
doi：10.1006/abbi.1999.1680
更新日期：2000-04-01 00:00:00
abstract：:Hyperammonemia is a major pathophysiological factor in encephalopathies associated with acute and chronic liver failure. On mouse brain slice preparations we analyzed the effects of ammonium on the characteristics of corticostriatal long-term potentiation (LTP) induced by high-frequency electrical stimulation (HFS) of...
journal_title：Archives of biochemistry and biophysics
pub_type： 杂志文章
doi：10.1016/j.abb.2013.02.002
更新日期：2013-08-15 00:00:00
abstract：:The nature of the purple complex formed upon the addition of octanoyl-CoA to the medium chain acyl-CoA dehydrogenase from pig kidney has been addressed by chemical quenching studies. Previous work, using quenching in 0.1 M KOH, suggested that the dehydrogenation product, trans-2-octenoyl-CoA, was not a participant in ...
journal_title：Archives of biochemistry and biophysics
pub_type： 杂志文章
doi：10.1016/0003-9861(88)90191-9
更新日期：1988-04-01 00:00:00
abstract：:Total liver poly(A+)-RNA isolated from untreated, and 3-methylcholanthrene-, trans-stilbene oxide-, and phenobarbital-treated rats has been translated in the rabbit reticulocyte lysate system in order to determine the effect of these xenobiotics on the level of translationally active DT-diaphorase mRNA. The in vitro t...
journal_title：Archives of biochemistry and biophysics
pub_type： 杂志文章
doi：10.1016/0003-9861(84)90556-3
更新日期：1984-07-01 00:00:00
abstract：:The rotating frame nuclear magnetic resonance relaxation rate R(1rho) in the blood and cell lysate was studied at 4.7T to provide reference values for in vivo modeling and to address the mechanisms contributing to net relaxation. A strong dependence on oxygenation, hematocrit, and spin lock field strength B(1) (0.2-1....
journal_title：Archives of biochemistry and biophysics
pub_type： 杂志文章
doi：10.1016/s0003-9861(02)00286-2
更新日期：2002-09-01 00:00:00
abstract：:Two isozymes of catalase (EC 1.11.1.6), one with typically low peroxidatic activity (CAT-1) and the other with enhanced-peroxidatic activity (EP-CAT or CAT-3) have been purified to electrophoretic homogeneity from tobacco (Nicotiana sylvestris) seedlings and antibodies prepared against each. The isozyme proteins showe...
journal_title：Archives of biochemistry and biophysics
pub_type： 杂志文章
doi：10.1016/0003-9861(90)90672-l
更新日期：1990-12-01 00:00:00
abstract：:Glyoxalase I, a member of the metalloglutathione (GSH) transferase superfamily, plays a critical detoxification role in cells by catalyzing the conversion of cytotoxic methylglyoxal (as the diastereomeric GSH-thiohemiacetals) to S-D-lactoylglutathione via a 1,2-hydrogen transfer. The mechanism-of-action of this Zn2+-m...
journal_title：Archives of biochemistry and biophysics
pub_type： 杂志文章,评审
doi：10.1006/abbi.2000.2253
更新日期：2001-03-01 00:00:00
abstract：:The ionophore properties of cationomycin and monensin were studied on human erythrocytes by measuring Na+ influx by 23Na NMR and concomitant K+ efflux by potentiometry in the presence of increasing amounts of serum. Both ion currents (Na+ or K+) decreased linearly with the reciprocal of serum amount. The serum effects...
journal_title：Archives of biochemistry and biophysics
pub_type： 杂志文章
doi：10.1006/abbi.1999.1101
更新日期：1999-03-15 00:00:00
abstract：:Transforming growth factor-beta (TGF-beta) reportedly induces vascular endothelial growth factor (VEGF) synthesis in osteoblast-like MC3T3-E1 cells. We have recently shown that TGF-beta activates p44/p42 mitogen-activated protein (MAP) kinase and p38 MAP kinase in these cells. In the present study, we investigated the...
journal_title：Archives of biochemistry and biophysics
pub_type： 杂志文章
doi：10.1016/s0003-9861(03)00225-x
更新日期：2003-07-01 00:00:00
abstract：:This study showcases the potential of unnatural amino acids to enable non-natural functions when incorporated in the protein scaffold of heme metalloproteins. For this purpose, a genetically-engineered myoglobin (Mb) mutant was created by incorporating redox-active 3-amino-l-tyrosine (NH2Tyr) into its active site, rep...
journal_title：Archives of biochemistry and biophysics
pub_type： 杂志文章
doi：10.1016/j.abb.2017.12.014
更新日期：2018-02-01 00:00:00
abstract：:The effect of transition from a respiring to a respiration-inhibited state on the rate of protein synthesis was investigated in glycolyzing, cultured rat heart cells. The rate was found to be significantly lower after blocking respiration, and it was further decreased by L-lactate. In contrast, pyruvate or phenazine m...
journal_title：Archives of biochemistry and biophysics
pub_type： 杂志文章
doi：10.1016/0003-9861(85)90615-0
更新日期：1985-01-01 00:00:00
abstract：:Most important processes in cell life are regulated by calcium (Ca2+). A number of mechanisms have thus been developed to maintain the concentration of free Ca2+ inside cells at the level (100-200nM) necessary for the optimal operation of the targets of its regulatory function. The systems that move Ca2+ back and fort...
journal_title：Archives of biochemistry and biophysics
pub_type： 杂志文章,评审
doi：10.1016/j.abb.2008.02.026
更新日期：2008-08-01 00:00:00
abstract：:Hyaluronan controls keratinocyte proliferation and regeneration. We examined effect of UV on the expression of hyaluronan synthases (HASs) and hyaluronidases in cultured normal human newborn foreskin epidermal keratinocytes, NHEK(F). HAS3 mRNA was expressed predominantly and HAS2 mRNA expressed in lesser amounts and b...
journal_title：Archives of biochemistry and biophysics
pub_type： 杂志文章
doi：10.1016/j.abb.2007.12.004
更新日期：2008-03-01 00:00:00
abstract：:Lipoxygenases react with hydroperoxy fatty acids and catalyze dioxygenase or dehydrase (leukotriene A4 (LTA4) synthase) types of reactions. In the present investigation we studied the mechanism of reaction of the purified porcine leukocyte 12S-lipoxygenase with 15S-hydroperoxyeicosatetraenoic acid (15S-HPETE). Oxygen-...
journal_title：Archives of biochemistry and biophysics
pub_type： 杂志文章
doi：10.1016/0003-9861(89)90500-6
更新日期：1989-09-01 00:00:00
abstract：:Phosphoenolpyruvate carboxylase from maize leaves was inactivated by pyridoxal 5'-phosphate in the dark and in the light. A two-step reversible mechanism is proposed for inactivation in the dark, which involves the formation of a noncovalent complex prior to a Schiff base with amino groups of the enzyme. Spectral anal...
journal_title：Archives of biochemistry and biophysics
pub_type： 杂志文章
doi：10.1016/0003-9861(86)90309-7
更新日期：1986-05-01 00:00:00
abstract：:Thyroid peroxidase (TPO) was purified from human thyroid tissue, obtained at surgery from patients with Graves' disease, by a procedure similar to one that we had previously used for the purification of porcine TPO. The membrane-bound enzyme was solubilized by treatment of the thyroid particulate fraction with trypsin...
journal_title：Archives of biochemistry and biophysics
pub_type： 杂志文章
doi：10.1016/0003-9861(90)90268-4
更新日期：1990-05-01 00:00:00
abstract：:Two forms of the beta-glucosidase amygdalin hydrolase (AH I and II), which catalyze the hydrolysis of (R)-amygdalin to (R)-prunasin and D-glucose, have been purified over 200-fold from mature black cherry (Prunus serotina Ehrh.) seeds. These proteins showed very similar molecular and kinetic properties but could be re...
journal_title：Archives of biochemistry and biophysics
pub_type： 杂志文章
doi：10.1016/0003-9861(86)90603-x
更新日期：1986-06-01 00:00:00
abstract：:The taxa-4(20),11(12)-dien-5alpha-ol-O-acetyl transferase which catalyzes the third step of Taxol biosynthesis has been isolated from methyl jasmonate-induced Taxus cells, and partially purified and characterized (K. Walker, R. E. B. Ketchum, M. Hezari, D. Gatfield, M. Golenowski, A. Barthol, and R. Croteau, Arch. Bio...
journal_title：Archives of biochemistry and biophysics
pub_type： 杂志文章
doi：10.1006/abbi.1999.1609
更新日期：2000-02-15 00:00:00
abstract：:Peroxynitrite crosses the red blood cell (RBC) membrane and reacts with hemoglobin (Hb) producing mainly metHb, which is reduced back to ferrousHb by NADH- and NADPH-dependent reductases. Peroxynitrite also induces band 3 (B3) tyrosine phosphorylation, a signaling pathway believed to activate glucose metabolism. This ...
journal_title：Archives of biochemistry and biophysics
pub_type： 杂志文章,评审
doi：10.1016/j.abb.2008.10.025
更新日期：2009-04-15 00:00:00
abstract：:Intensively treating type I diabetics with continuous subcutaneous insulin infusions or multiple daily insulin injections to normalize mean blood glucose concentrations significantly reduces the onset of secondary diabetic complications when compared to conventionally treated diabetics. Our studies focused on characte...
journal_title：Archives of biochemistry and biophysics
pub_type： 杂志文章
doi：10.1006/abbi.1999.1299
更新日期：1999-08-15 00:00:00
abstract：:60S ribosomal protein L35 (RPL35) is an important component of the 60S ribosomal subunit and has a role in protein translation and endoplasmic reticulum (ER) docking. However, few studies have investigated RPL35 in eukaryotes and much remains to be learned. Here, we analyzed the function of RPL35 in β-casein (CSN2) sy...
journal_title：Archives of biochemistry and biophysics
pub_type： 杂志文章
doi：10.1016/j.abb.2015.08.006
更新日期：2015-10-01 00:00:00
abstract：:Selenium compounds that contain selenol functions or can be metabolized to selenols are toxic via superoxide and H2O2 generation, when ingested at dosages beyond requirement. At supra-nutritional dosages various forms of programmed cell death are observed. At physiological intakes, selenium exerts its function as cons...
journal_title：Archives of biochemistry and biophysics
pub_type： 杂志文章,评审
doi：10.1016/j.abb.2016.08.003
更新日期：2017-03-01 00:00:00
abstract：:The specific tyrosine phosphorylation of glucose-6-phosphate dehydrogenase (G6PDH) by the epidermal growth factor (EGF) receptor in vitro is demonstrated. The Km values of the substrate G6PDH and of ATP for the receptor tyrosine kinase were ca. 1 and 10 microM, respectively. The rate of phosphorylation was EGF depende...
journal_title：Archives of biochemistry and biophysics
pub_type： 杂志文章
doi：10.1016/0003-9861(87)90496-6
更新日期：1987-12-01 00:00:00
