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Dive into the research topics where Henry Z. Sable is active.

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Featured researches published by Henry Z. Sable.


Archives of Biochemistry and Biophysics | 1975

Enzymes of pentose biosynthesis. The quaternary structure and reacting form of transketolase from baker's yeast☆

Susan W. Cavalieri; Kenneth E. Neet; Henry Z. Sable

Abstract Transketolase from bakers yeast is a dimeric enzyme with a molecular weight of 158,000 ± 4000. Sedimentation velocity and sedimentation equilibrium experiments indicate that the enzyme dissociates at low concentrations (less than 0.1 mg/ml) in the absence of the coenzyme, thiamine pyrophosphate. However, no such dissociation was detected in the presence of coenzyme. Reacting enzyme sedimentation velocity measurements showed that the reacting species of the enzyme is a dimer with an s20,w of 7.7 S.


Carbohydrate Research | 1967

Studies on cyclic polyols : Part IV. Nuclear magnetic resonance spectra and configurational assignments of polyhydroxycyclopentanes

Henry Z. Sable; William M. Ritchey; J. Eric Nordlander

Abstract The configurations of five cyclopentanetetrols and both 3,5-cyclopentenediols have been established by examination of their n.m.r. spectra. The configurational assignments are based to a large extent on the nature of the methylene signals (A 2 X 2 , ABX 2 or ABXY), and in one case the magnitude of the vicinal coupling constant is used as the basis of assigning the 1, sol4 2 ,3 structure in preference to the all- cis configuration. The present conclusions confirm earlier assignments based on purely chemical grounds. Spectral data for the ring protons of the tetrol tetrabenzoates, diols, epoxydiols and corresponding dibenzoates, a dibromoglycol and several O -isopropylidene derivatives of cyclopentanepolyols are presented. The internal chemical shifts between the A, B and X protons of the ABX 2 system observed in many of these compounds have been studied. The internal shifts δ x δ a and δ x δ b agree well with the internal shifts reported for the ABX system in two series of substituted bicyclo[2.2.1]heptenes. The linear variation of internal chemical shift with electronegativity of the substituent and the angular dependence of deshielding found in the bicycloheptenes is thus also found in the cyclopentanes. Unlike the case of the bicycloheptenes, which are rigid, the coupling constants J ax , J bx and J ab do not vary linearly with the electronegativity of the substituents, presumably because of the additional factor of variability of the dihedral angles in the various cyclopentanes, due to the greater flexibility of these molecules.


Analytical Biochemistry | 1974

Pitfalls in the study of steady state kinetics of enzymes: Spurious inhibition patterns due to stray light errors☆

Ralph L. Cavalieri; Henry Z. Sable

Abstract When reaction velocity measurements of enzyme reactions are carried out with single beam, single monochromator spectrophotometers, stray light in the spectrophotometer can produce systematic errors in the apparent velocities when highly absorbing solutions (optical density >2.0) are used. These errors can give rise to spurious “inhibition” patterns of the steady state kinetics. Because of a suspected error of this kind, this laboratory has recently reinvestigated the kinetics of glucose 6-phosphate dehydrogenase from Escherichia coli and found that the reported noncompetitive inhibition of the enzyme by DPNH is explained more readily by an unnoticed effect of stray light on the apparent reaction velocity than by a true enzyme inhibition. Methods for estimating and correcting such errors in spectrophotometers are presented in detail.


Biochemical and Biophysical Research Communications | 1971

Magnetic resonance study of the Mn2+ - lysozyme complex

Anthony A. Gallo; T.J. Swift; Henry Z. Sable

Summary The binding of Mn 2+ to lysozyme has been determined (a) by measurement of the longitudinal relaxation rate of water protons in aqueous solutions containing lysozyme, MnCl 2 and Tris or acetate buffer; and (b) by examination of EPR spectra. The competition between Mn 2+ and Co 2+ for binding to lysozyme was also investigated. The data are consistent with a lysozyme - Mn 2+ complex involving Asp-52 and Glu-35. Contrary to the expected order of stability of Co 2+ and Mn 2+ coordination complexes with nitrogen and oxygen donor atoms, Mn 2+ binds more strongly than Co 2+ . Both Mn 2+ and Co 2+ are inhibitors of lysozyme activity.


Biochimica et Biophysica Acta | 1983

The properties of membranes formed from cyclopentanoid analogues of phosphatidylcholine

Michael A. Singer; Mahendra Kumar Jain; Henry Z. Sable; Henry J. Pownall; William W. Mantulin; Mark D. Lister; Anthony J. Hancock

We have examined the thermal characteristics and barrier properties of vesicles formed from six analogues of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC). These analogues differ from DPPC in that the glycerol backbone has been replaced by each of the diastereoisomeric cyclopentane-1,2,3-triols. All of these compounds have main gel to liquid-crystal phase transition temperatures within 5 Kelvin of DPPC and four possess comparable enthalpies and entropies of transition. For two of the analogous, however, the values of the enthalpy and entropy of transition are more than double that of DPPC. The permeability characteristics and organization (as measured by diphenylhexatriene fluorescence depolarization) of vesicles formed from these two compounds suggest that their large transition enthalpy and entropy result from either a reorganization of the polar head group region during the transition or interdigitation of the acyl chains of opposing monolayers.


Biochimica et Biophysica Acta | 1973

Rate enhancement of pyruvate aldolization by divalent cations: A model for class II aldolases

Anthony A. Gallo; Henry Z. Sable

Abstract Zn 2+ catalysis of pyruvate aldolization is approx. 10 5 times more effective than water at pH 6.4. The reaction is first order in pyruvate and general base catalyzed, suggesting that enolization of pyruvate is rate limiting. As a result of the high efficiency Zn 2+ catalysis, the half life of a 1.0 M pyruvate solution containing 24 mM Zn 2+ , pH 6.4, is only 37 min. Mg 2+ and Ca 2+ are much less effective than Cu 2+ , Zn 2+ , Co 2+ or Ni 2+ . The great enhancement of pyruvate aldolization by Zn 2+ lends support to a previously suggested model of Class II (metallo) aldolase reactions in which coordination of metal ions to the carbonyl oxygen of the substrate labilizes the α-carbon-hydrogen bond. Metal ions present in stock solutions of pyruvate at concentrations high enough to catalyze significant amounts of aldolization may lead to complications when pyruvate-containing assay mixtures are used in enzyme studies, since the aldol dimer of pyruvate is a potent inhibitor of the citric acid cycle.


Chemistry and Physics of Lipids | 1990

Cyclopentanoid analogs of dipalmitoyl phosphatidic acid: effect of backbone geometry on thermotropic properties.

Tareq Y. Ahmad; Joel D. Morrisett; Henry J. Pownall; Antonio M. Gotto; Howard L. Brockman; Henry Z. Sable; Everett O. Lewis; Anthony J. Hancock

Seven geometrical or positional isomers of dipalmitoyl cyclopentanophosphoric acid (DPCPA) have been synthesized and studied: 1,3/2-1P (I); 1,2/3-1P (II); 1,2/3-3P (III), 1,2,3/0-1P (IV); 1,2,3/0-2P (V); 1,3/2-2P (VI); 1,2/3-2P (VII). When dispersed in 0.1 M Tris-HCl at pH 7.4, I-VII gave thermal transitions (Tc) of 60.0 degrees, 59.0 degrees, 56.8 degrees, 55.3 degrees, 38.3 degrees, 36.8 degrees and 34.0 degrees C, respectively, as measured by differential scanning calorimetry (DSC). When the lipids were dispersed at pH 9.5 in 0.1 M borate, Tc of I-IV decreased, whereas Tc of V-VII increased. In contrast, at pH 1.5 in 0.1 M HCl/KCl, Tc of I-IV decreased slightly, but Tc of V-VII rose markedly. To determine the effect of head group geometry and substitution pattern on acyl chain motion, EPR spectra of 1-palmitoyl, 2-[16-doxylstearoyl]-glycero-3-phosphoric acid in bilayers of DPCPA isomers were acquired. Abrupt spectral changes occurred at temperatures closely correlating with transition temperatures observed by DSC. These results have led to the conclusions that: (i) isomers I-IV containing vicinal acyl chains form bilayers that exhibit structural transitions at temperatures higher than those at which transitions are exhibited by isomers V-VII which have a polar phosphate group interposed between the two chains; (ii) the effects of differences in backbone structure are transmitted down the entire length of the acyl chains; (iii) the orientation of the cyclopentane ring in the isomers I-IV is significantly different from that in isomers V-VII at pH values where the phosphate group is doubly negatively charged.


Spectroscopy Letters | 1969

Studies on Cyclitols. XIV. Methyl Group Signals of gem-Dimethyldioxolanes as Indicators of Anisotropy

Henry Z. Sable; William M. Ritchey; J. Eric Nordlander

Abstract In connection with our interest in nmr spectroscopy of cyclopentanoid and 2, 4-dioxabicyclo[3. 3. 0] octane systems3 we have synthesized a large number of gem-dimethyldioxolanes2,4 and have examined their spectra. The spectra of all the compounds showed two distinct singlets, representing the two methyl groups, in the region δ 1. 2-1. 5. Similar values have been reported in the case of derivatives of 1, 2-O-isopropylidene-α-D-xylohexofuranose by Abraham et al.5 Perlin6 has reported similar differences in the chemical shift of the endo- and exo- C-methyl groups of the diastereoisomeric orthoacetates of D-mannose, and Baggett et al.7 observed a difference of 0. 30 ppm between the chemical shifts of endo- and exo-benzyl protons of O-benzylidene sugars. Our studies permit the assignment of the lower field resonance to the endo-methyl group and the higher field resonance to the exo-methyl group of the dimethyldioxolanes.


Chemistry and Physics of Lipids | 1977

Analogs of natural lipids. II. Polymorphic behavior of the tris-Homo acyl derivatives of cyclopentane-1,2,3-triols

S.M. Greenwald; A.J. Hancock; Henry Z. Sable; L. D'esposito; J.L. Koenig

The polymorphic behavior of three series of tris-homoacyl (C14:0, C16:0 and C18:0) cyclopentane-1,2,3-triol analogs of the natural saturated triglycerides has been studied using differential thermal analysis, Fourier transform infrared spectroscopy, and X-ray diffraction. It was found that the triglyceride analogs derived from the 1,2,3/0 and 1,2/3 cyclopentanetriols exhibit different polymorphic behavior than that of the natural triglycerides. The analogs derived from 1,3/2 cyclopentanetriol, however, were found to parallel the polymorphic behavior of the natural triglycerides quite closely. This polymorphic behavior is discussed in terms of the different configurations which the chains assume in each of the triglyceride analogs.


Archive | 1979

Studies on the Mechanism of Catalysis by Thiamin: Progress and Problems

Henry Z. Sable; Debra J. Meschke

The mechanism of catalysis by thiamin is discussed with respect to the function of the NH2 group. Hypotheses that assume that the NH2 group behaves as an intramolecular general base are untenable because such amino groups are not basic. On the contrary, many lines of evidence show that the NH2 groups of aminopurines and aminopyrimidines should be considered as Lewis acids. The evidence includes the following: the π-electronic charge density is low; in H-bond formation these NH2 groups are H-donors and never H-acceptors; rate constants for specific acid- and specific base-catalyzed exchange of the NH2 protons with solvent water are 106 –108 and 102 times smaller, respectively, than those for the corresponding diffusion-controlled reactions. A catalytic mechanism involving a Lewis acid is proposed. The exchange of the thiazolium (C-2) proton with solvent has been reinvestigated by two NMR methods: (a) disappearance of the signal of (C-2)H in D2O due to H—D exchange; (b) broadening of the (C-2)H signal in H2O solution due to H—H exchange. Rates calculated from the latter method are approximately two orders of magnitude larger than those from H—D exchange.

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Anthony A. Gallo

Case Western Reserve University

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Anthony J. Hancock

University of Missouri–Kansas City

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John J. Mieyal

Case Western Reserve University

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Elmer M. Wright

Case Western Reserve University

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J. Eric Nordlander

Case Western Reserve University

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William M. Ritchey

Case Western Reserve University

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Henry J. Pownall

Houston Methodist Hospital

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