Abstract:
:Isotope effects have been measured with Mg2+ as the activator and L-malate labeled with deuterium or tritium at carbon 2 as the substrate over the pH range 4-10. Comparison of the nearly pH-independent deuterium-isotope effect on V/Kmalate of 1.5 with the tritium effect of 2.0 by the method of Northrop (Northrop, D.B. (1975), Biochemistry 14, 2644) gives limits on the true effect of deuterium substitution on the bond-breaking step of 5-8 in the forward reaction and 4-6.5 in the reverse direction. Comparison of the deuterium effect on V/K with the 13C-isotope effect of 1.031 reported by Schimerlik et al. (Schimerlik, M.I., Rife, J.E., and Cleland, W.W. (1975), Biochemistry 14, 5347) allows the deduction that at pH 8 reverse hydride transfer is six to eight times faster than decarboxylation, which is thus largely rate limiting for the catalytic reaction. The absence of a deuterium-isotope effect on V at pH 7-8 and comparison of the Ki of pyruvate as an uncompetitive inhibitor of the forward reaction and a substrate for the reverse reaction indicate that at neutral pH the release of TPNH from enzyme-reduced triphosphopyridine nucleotide (E-TPNH) is the rate-limiting step in the forward direction. The observation of a deuterium effect on V that approaches 3 at pH 4 and 10 shows, however, that, at very low and very high pH, hydride transfer may become partly rate limiting. In the reverse reaction, the probable rate-limiting step at pH 7 is the isomerization of E-TPNH, while at pH 8.5 and above V becomes too large to measure and appears infinite. Substitution of Co2+, Ni2+, or low levels of Mn2+ for Mg2+ gives similar deuterium-isotope effects, although the values of V and Kmalate vary considerably with metal. The kinetics of Mn2+ show pronounced negative cooperativity, with Km values of 7 muM and 5 mM for concentration ranges from 4 to 100 muM and over 1 mM.
journal_name
Biochemistryjournal_title
Biochemistryauthors
Schimerlik MI,Grimshaw CE,Cleland WWdoi
10.1021/bi00623a002subject
Has Abstractpub_date
1977-02-22 00:00:00pages
571-6issue
4eissn
0006-2960issn
1520-4995journal_volume
16pub_type
杂志文章相关文献
BIOCHEMISTRY文献大全abstract::An OxlT homology model suggests R272 and K355 in transmembrane helices 8 and 11, respectively, are critical to OxlT-mediated transport. We offer positive evidence supporting this idea by studying OxlT function after cysteine residues were separately introduced at these positions. Without further treatment, both mutant...
journal_title:Biochemistry
pub_type: 杂志文章
doi:10.1021/bi060746v
更新日期:2006-08-29 00:00:00
abstract::Homing endonucleases are distinguished by their ability to catalyze the cleavage of double-stranded DNA with extremely high specificity. I-PpoI endonuclease, a homing endonuclease from the slime mold Physarum polycephalum, is a small enzyme (2 x 20 kDa) of known three-dimensional structure that catalyzes the cleavage ...
journal_title:Biochemistry
pub_type: 杂志文章
doi:10.1021/bi991452v
更新日期:1999-12-07 00:00:00
abstract::A total of fifty single site surface phenylalanine substitution mutants have been made in the model protein staphylococcal nuclease. The fifty residues that were replaced with phenylalanine were chosen to give a broad sampling of solvent accessibility, secondary structure, and backbone conformations. The change in the...
journal_title:Biochemistry
pub_type: 杂志文章
doi:10.1021/bi9725069
更新日期:1998-05-12 00:00:00
abstract::We have covalently attached an electron paramagnetic resonance (EPR) spin probe to Cys-670 of the motor domain of ncd (nonclaret disjunctional protein) in order to investigate conformational changes associated with the chemomechanical cycle. Spin-labeling is highly specific and does not affect ncd function as monitore...
journal_title:Biochemistry
pub_type: 杂志文章
doi:10.1021/bi9706881
更新日期:1997-08-12 00:00:00
abstract::The dynamics of the backbone and (some of) the side chains of lac headpiece (1-56; lac HP56) have been studied for the free protein and for its complex with lac half-operator DNA by 15N T1 and T1p relaxation measurements combined with [1H-15N] NOE experiments. For the structurally well-defined part of the free lac HP5...
journal_title:Biochemistry
pub_type: 杂志文章
doi:10.1021/bi961670d
更新日期:1997-01-07 00:00:00
abstract::Sso7d from the thermoacidophilic archaebacterium Sulfolobus solfataricus is a small globular protein with a known three-dimensional structure. Inspection of the structure reveals that Phe31 is a member of the aromatic cluster forming the protein hydrophobic core, whereas Trp23 is located on the protein surface and its...
journal_title:Biochemistry
pub_type: 杂志文章
doi:10.1021/bi972994k
更新日期:1998-07-21 00:00:00
abstract::Preferential interaction of trans-membrane alpha-helices whose hydrophobic length matches the hydrophobic thickness of the lipid bilayer could be a mechanism of retention in the Golgi apparatus. We have used fluorescence methods to study the interaction of peptides Ac-K2-G-Lm-W-Ln-K2-A-amide (Pm+n) with bilayers of ph...
journal_title:Biochemistry
pub_type: 杂志文章
doi:10.1021/bi972441+
更新日期:1998-01-13 00:00:00
abstract::By using targeted disulfide cross-linking, we have characterized structural changes that the Escherichia coli aspartate receptor undergoes upon modification of the four specific residues that are reversibly methylated during sensory adaptation. Cysteine residues were introduced at specific positions either in the cyto...
journal_title:Biochemistry
pub_type: 杂志文章
doi:10.1021/bi980343y
更新日期:1998-10-20 00:00:00
abstract::Malate dehydrogenase occurs in virtually all eucaryotic cells in mitochondrial and cytoplasmic forms, both of which are composed of two identical subunits. The reactivation of the mitochondrial isoenzyme has been the subject of previous studies [Jaenicke, R., Rudolph, R., & Heider, I. (1979) Biochemistry 18, 1217-1223...
journal_title:Biochemistry
pub_type: 杂志文章
doi:10.1021/bi00355a033
更新日期:1986-04-08 00:00:00
abstract::Binding mechanisms of ADPR-transferase to restricted double-stranded DNA fragments of SV40 and pBR322 DNA were determined by nuclease protection techniques. Top and bottom strands of double-stranded DNA were identified by specific labeling with 32P. Protection against specific exonucleases identified binding of ADPR-t...
journal_title:Biochemistry
pub_type: 杂志文章
doi:10.1021/bi00439a050
更新日期:1989-06-27 00:00:00
abstract::Pea histones H2a, H2b, H3, and H4 have been isolated and their interactions studied by fluorescence anisotropy, light scatter, and circular dichroism. Histones H3 and H4 are almost identical in plants and animals, but plant histones H2a and H2b differ markedly from their mammalian counterparts. Pea H2b has a molecular...
journal_title:Biochemistry
pub_type: 杂志文章
doi:10.1021/bi00628a009
更新日期:1977-05-03 00:00:00
abstract::The activity of the phosphoenolpyruvate-dependent glucose phosphotransferase system (PTS) in Escherichia coli is coupled to the oxidation-reduction potential. It is inhibited when the redox potential is increased above -300 mV either via substrate oxidation or via direct addition of oxidizing agents. Depending on the ...
journal_title:Biochemistry
pub_type: 杂志文章
doi:10.1021/bi00520a032
更新日期:1981-08-18 00:00:00
abstract::The solution conformation of potato carboxypeptidase inhibitor (CPI) has been investigated by 1H NMR spectroscopy. The spectrum is assigned in a sequential manner by using two-dimensional NMR techniques to identify through-bond and through-space (less than 5 A) connectivities. A set of 309 approximate interproton dist...
journal_title:Biochemistry
pub_type: 杂志文章
doi:10.1021/bi00398a069
更新日期:1987-12-01 00:00:00
abstract::S-Protein/vitronectin is a serum glycoprotein that inhibits the lytic activity of the membrane attack complex of complement, i.e., of the complex including the proteins C5b, C6, C7, C8, and C9n. We show that intact S-protein/vitronectin or its cyanogen bromide generated fragments also inhibit the hemolysis mediated by...
journal_title:Biochemistry
pub_type: 杂志文章
doi:10.1021/bi00411a029
更新日期:1988-05-31 00:00:00
abstract::Subunit a of the Escherichia coli ATP synthase is thought to control access of protons to the ring of c subunits during proton-driven ATP synthesis. In this study, the surface exposure of subunit a in the periplasm has been examined using 3-N-maleimidyl-propionyl biocytin labeling in cells permeabilized by polymyxin B...
journal_title:Biochemistry
pub_type: 杂志文章
doi:10.1021/bi026649t
更新日期:2003-01-21 00:00:00
abstract::Recent models for water oxidation in photosystem II postulate that the tyrosine Y(Z) radical, Y(Z)(*), abstracts both an electron and a proton from the Mn cluster during one or more steps in the catalytic cycle. This coupling of proton- and electron-transfer events is postulated to provide the necessary driving force ...
journal_title:Biochemistry
pub_type: 杂志文章
doi:10.1021/bi992749w
更新日期:2000-05-30 00:00:00
abstract::Using solution peptide synthesis, we have made three series of N alpha-formylated homooligopeptides, from the dipeptide to the heptapeptide, derived from L-methionine, L-norleucine, and S-methyl-L-cysteine and related to the chemotactic peptide N alpha-formylmethionylleucylphenylalanine. Compounds were prepared to det...
journal_title:Biochemistry
pub_type: 杂志文章
doi:10.1021/bi00299a018
更新日期:1984-02-14 00:00:00
abstract::Cytochrome P450 3A4 is a drug-metabolizing enzyme of extraordinarily broad substrate specificity. This quality imparts upon the enzyme special importance in understanding its determinants of activity and substrate recognition. Limited successes in P450 3A4 active-site structure studies have been achieved by use of mec...
journal_title:Biochemistry
pub_type: 杂志文章
doi:10.1021/bi049231z
更新日期:2005-02-15 00:00:00
abstract::Protein electrochemistry in an ultra-thin-layer electrochemical cell suitable for UV/vis and IR spectroscopy has been used to characterize the vibrational modes of the primary electron donors of Rhodobacter sphaeroides and Rhodopseudomonas viridis reaction centers in their neutral and cation radical states (P and P+, ...
journal_title:Biochemistry
pub_type: 杂志文章
doi:10.1021/bi00068a007
更新日期:1993-05-04 00:00:00
abstract::This paper characterizes the low-affinity ligand binding interactions of a fluorinated volatile anesthetic, isoflurane (CHF2OCHClCF3), with bovine serum albumin (BSA) using 19F-NMR transverse relaxation (T2). 19F-NMR spectra of isoflurane in aqueous BSA reveal a single isoflurane trifluoromethyl resonance, indicative ...
journal_title:Biochemistry
pub_type: 杂志文章
doi:10.1021/bi00146a007
更新日期:1992-08-11 00:00:00
abstract::Flavin-dependent histone demethylases catalyze the posttranslational oxidative demethylation of mono- and dimethylated lysine residues, producing formaldehyde and hydrogen peroxide in addition to the corresponding demethylated protein. In vivo, histone demethylase LSD1 (KDM1; BCH110) is a component of the multiprotein...
journal_title:Biochemistry
pub_type: 杂志文章
doi:10.1021/bi101776t
更新日期:2011-02-01 00:00:00
abstract::A gentle and rapid isolation procedure is described yielding fractions containing better than 95% pure OmpF porin of Escherichia coli BE with different amounts of bound lipopolysaccharide (LPS). The procedure employs continuous free-flow electrophoresis (FFE) in the presence of detergent above its critical micelle con...
journal_title:Biochemistry
pub_type: 杂志文章
doi:10.1021/bi00436a010
更新日期:1989-05-16 00:00:00
abstract::Multimodular enzymes, including polyketide synthases (PKSs), nonribosomal peptide synthetases (NRPSs), and mixed PKS/NRPS systems, contain functional domains with similar functions. Domain swapping and module fusion are potential powerful strategies for creating hybrid enzymes to synthesize modified natural products. ...
journal_title:Biochemistry
pub_type: 杂志文章
doi:10.1021/bi047538s
更新日期:2005-03-29 00:00:00
abstract::The role of ATP hydrolysis by the 44/62 protein in formation of the stable holoenzyme DNA replication complex has been further elucidated by specifically examining the role that the 44/62 protein plays in loading the 45 protein onto the DNA substrate. A stable phospho-45 protein or phosphorylated holoenzyme complex wa...
journal_title:Biochemistry
pub_type: 杂志文章
doi:10.1021/bi962139l
更新日期:1997-03-11 00:00:00
abstract::Glutamate151 (E151) has been shown to be catalytically essential for the aminopeptidase from Vibrio proteolyticus (AAP). E151 acts as the general acid/base during the catalytic mechanism of peptide hydrolysis. However, a glutamate residue is not the only residue capable of functioning as a general acid/base during cat...
journal_title:Biochemistry
pub_type: 杂志文章
doi:10.1021/bi0505823
更新日期:2005-09-13 00:00:00
abstract::The influence of membrane pH gradients on the transbilayer distribution of some common phospholipids has been investigated. We demonstrate that the transbilayer equilibrium of the acidic phospholipids egg phosphatidylglycerol (EPG) and egg phosphatidic acid (EPA) can be manipulated by membrane proton gradients, wherea...
journal_title:Biochemistry
pub_type: 杂志文章
doi:10.1021/bi00436a009
更新日期:1989-05-16 00:00:00
abstract::We have investigated, both experimentally and theoretically, the efflux of carboxyfluorescein (a self-quenching fluorescent dye) from vesicles of different sizes and lipid species (POPC, DOPC) after having added the bee venom peptide melittin. This comprises quantitative analyses regarding the extent of lipid-associat...
journal_title:Biochemistry
pub_type: 杂志文章
doi:10.1021/bi971009p
更新日期:1998-02-24 00:00:00
abstract::Using our Escherichia coli expression system, we have produced five mutant recombinant (r) hemoglobins (Hbs): r Hb (alpha V96 W), r Hb Presbyterian (beta N108K), r Hb Yoshizuka (beta N108D), r Hb (alpha V96W, beta N108K), and r Hb (alpha V96W, beta N108D). These r Hbs allow us to investigate the effect on the structur...
journal_title:Biochemistry
pub_type: 杂志文章
doi:10.1021/bi990286o
更新日期:1999-07-06 00:00:00
abstract::We have studied the hydrogen-exchange kinetics of hemoglobin A0 as a function of ligand, CO, saturation. In the noncooperative system, azide binding to methemoglobin, the alterations in exchange kinetics are proportional to the average degree of ligation. However, in the case of CO binding to deoxyhemoglobin the chang...
journal_title:Biochemistry
pub_type: 杂志文章
doi:10.1021/bi00297a015
更新日期:1984-01-17 00:00:00
abstract::Apolipoprotein (apo) B, the major protein component of the atherogenic low-density lipoprotein (LDL), has a pentapartite structure, NH2-betaalpha1-beta1-alpha2-beta2-alpha3-COOH, the beta domains containing multiple amphipathic beta strands and the alpha domains containing multiple amphipathic alpha helixes. We recent...
journal_title:Biochemistry
pub_type: 杂志文章
doi:10.1021/bi011757l
更新日期:2002-06-04 00:00:00