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PubMed1993

[Effect of Na-L-glutamate on mitochondrial function of ATP synthesis after prolonged preservation in rat heart].

We studied the effect of Na-L-glutamate (Glu) on mitochondrial functions of ATP synthesis after prolonged hypothermic preservation of rat hearts. We divided isolated rat hearts into the following three groups: group A, hearts without immersion as control; group B, hearts immersed in Euro-Collins solution (E-C) without Glu for 24 h at 4 degrees C; group C, hearts immersed in E-C with 10mM Glu for 24 h at 4 degrees C. Number of each group used was 6. Mitochondrial functions of ATP production were determined by measuring respiratory control index (RCI). P/O ratio and state III respiration rate. The ability of ATP production (oxidative phosphorylation rate, OPR) was calculated. RCI and P/O ratio of groups B and C were significantly lower than those of group A. RCI and P/O ratio of group C were significantly higher than that of group B. S3 rates of groups B and C were significantly lower than those of group A. S4 rate of group B was significantly higher than those of groups A and C. OPRs of groups B and C were significantly lower than that of group A. OPR of group C was significantly higher than that of group B. We concluded that Na-L-glutamate effectively protected mitochondrial functions to synthesize ATP during prolonged hypothermic preservation.

Adenosine Triphosphate↗

PubMed1993

A role for the mitochondrial Na(+)-Ca2+ exchanger in the regulation of oxidative phosphorylation in isolated heart mitochondria.

The role of the Na(+)-Ca2+ exchanger of heart mitochondria in cellular functioning is not yet clear. The objectives of this study were to investigate the effects of stimulation and inhibition of the Na(+)-Ca2+ exchanger on the matrix free Ca2+ concentration in isolated heart mitochondria and to determine the consequences of these changes on the rate of NADH production via Krebs cycle turnover and the oxidative phosphorylation rate (OPR) supported by alpha-ketoglutarate dehydrogenase, a Ca(2+)-regulated matrix enzyme. Activation of Na(+)-Ca2+ exchange by increasing extramitochondrial Na+ concentration was found to decrease the matrix free [Ca2+] in a concentration-dependent manner. Inhibitors of mitochondrial Na(+)-Ca2+ exchange activity inhibited the decrease in matrix free [Ca2+] mediated by Na+. Increasing concentrations of Na+ were also found to inhibit both the rate of NADH production and OPR. Inhibitors of mitochondrial Na(+)-Ca2+ exchange also blocked the effects of Na+ on the rate of NADH production and OPR in a similar concentration range. The results indicate that alterations in matrix free [Ca2+] induced by changes in mitochondrial Na(+)-Ca2+ exchange activity are translated into changes in the rate of NADH production and the overall rate of oxidative phosphorylation.

Animals↗

PubMed1997

Enhanced brain opioid receptor activity precedes blood-brain barrier disruption.

We studied the effects of transient postischemic increased opioid receptors (OPR) binding (mu, delta, kappa) on blood-brain barrier (BBB), brain water content and brain mitochondrial oxidative enzymes system. Cats were exposed to temporary middle cerebral artery occlusion (MCAO). The significant increased OPR bindings observed 10 min after the release of MCAO (ischemic rCBF = 7 +/- 1 to 11 +/- 2 ml/100 g/min) preceded the early and late BBB disruptions, brain edema and postischemic impaired mitochondrial oxidative enzymes functions. Further, the study suggests indirectly that the latter process was irreversible and hence associated with subsequent ischemic cerebral infarction. In addition, the results revealed a possible viable therapeutic window in the early postischemic recirculation period, before the onset of impaired mitochondrial oxidative function.

Animals↗

PubMed1999

Structure and regulation of OPR1 and OPR2, two closely related genes encoding 12-oxophytodienoic acid-10,11-reductases from Arabidopsis thaliana.

The genes of two closely related 12-oxophytodienoic acid reductases (EC 1.3.1.42), OPR1 and OPR2, were identified on a 7079-bp-long genomic fragment from Arabidopsis thaliana (L.) Heynh. The organization of these two genes was determined and putative cis elements were identified. Promoter-beta-glucuronidase (GUS) fusions expressed in transgenic Arabidopsis thaliana and Nicotiana tabacum L. plants revealed differences in OPR-promoter-driven GUS expression in flowers. While the OPR1 promoter directed GUS expression in young seeds, the OPR2 promoter directed pollen-specific expression. Both OPR1 and OPR2, were predominantly expressed in roots. Stress treatments, like local and systemic wounding, UV-C illumination and coldness, resulted in transient changes in steady-state OPR mRNA levels, but no concurrent changes in polypeptide level or enzyme activity were detected.

Arabidopsis↗

PubMed1995

Synthesis of a thio analogue of n-propyl kojibioside, a potential glucosidase inhibitor.

The disaccharide alpha-D-Glc p-(1-S-2)-beta-D-Glc p-(1-OPr) 1, a thio analogue of alpha-D-Glc p-(1 --> 2)-alpha-D-Glc p-(1-OPr)(n-propyl kojibioside) in which the inter-glycosidic oxygen atom is replaced by sulfur, has been synthesized for evaluation as a potential glucosidase inhibitor. Glycosylation of the 2-thiol glucopyranosyl acceptor 4 with the trichloroacetimidate of 2,3,4,6-tetra-O-benzyl-alpha-D-glucopyranose 5 gave the alpha-linked disaccharide 6 stereoselectively. Deprotection was performed by hydrogenolysis in the presence of Pd/C to give 1 as the beta-n-propyl glycoside. Glycosylation of the thiol 4 with the trichloroacetimidate of 2,3,4,6-tetra-O-acetyl-alpha-D-glucopyranose 8 gave a 1:2.3 mixture if the alpha and beta disaccharides (9 and 10); evidence is presented for the occurrence of the orthoester 11, as an intermediate in the formation of the beta-disaccharide.

Carbohydrate Sequence↗

PubMed2004

Synthetic human prion protein octapeptide repeat binds to the proteinase K active site.

Proteinase K is widely used in tests for the presence of infectious prion protein causing fatal spongiform encephalopathies. To investigate possible interactions between the enzyme and the functionally important N-terminal prion domain, we crystallized mercury-inhibited proteinase K in the presence of the synthetic peptides GGGWGQPH and HGGGW. The octapeptide sequence is identical to that of a single octapeptide repeat (OPR) from the physiologically important OPR region. Here, we present the first direct evidence for the complex formation between a proteolytic enzyme and a segment of human prion molecule. The X-ray structures of the complexes at 1.4 and 1.8A resolution, respectively, revealed that in both cases the segment GGG is strongly bound as a real substrate at the substrate recognition site of the proteinase forming an antiparallel beta-strand between the two parallel strands of Asn99-Tyr104 and Ser132-Gly136. The complex is stabilized through an extended H-bonding network.

Binding Sites↗

PubMed2006

Sol-gel processing of a bimetallic alkoxide precursor confined in a porous glass matrix: a route to novel glass/metal oxide nanocomposites.

In this work we present the utilization of the heterometallic alkoxide [FeCl{Ti(2)(OPr(i))(9)}] as the first sol-gel single-source precursor to achieve nanocomposites made of iron and titanium oxides incorporated into Porous Vycor Glass (PVG). The nanocomposites were prepared by the impregnation of the precursor in a PVG plate followed by hydrolysis reactions. Different samples were obtained by further thermal treatment of the hydrolyzed sample. The nanocomposites were characterized by UV-vis-NIR, Raman and EPR spectroscopies, XRD and TEM. The results indicate that the room-temperature hydrolyzed samples are formed by nanoparticles of FeOOH and brookite-TiO(2) embedded on a glassy matrix. After the heat treatment at temperatures above 900 degrees C, a pseudobrookite Fe(2)TiO(5) was formed. All samples present high transparency and homogeneity. The results showed here indicate that the sol-gel process using the single-source precursor [FeCl{Ti(2)(OPr(i))(9)}] should be a novel and efficient approach to the preparation of nanometric Fe/Ti oxides incorporated into a glassy matrix.

Journal Article↗

PubMed1996

Effect of physical training on mitochondrial function in skeletal muscle of normal and diabetic rats.

The study was designed to assess the impact of physical training on the oxidative phosphorylation rate (OPR) in mitochondria isolated from two different skeletal muscles of rats with or without chronic diabetes mellitus. Diabetes was induced by an intravenous injection of streptozotocin (50 mg/kg), and only animals with a blood glucose level between 14 and 22 mmol/L 1 week later were kept in the protocol. Exercise training was performed on a treadmill with a progressive 10-week program. Rats were killed by decapitation at the end of the training program, and mitochondria were isolated from the gastrocnemius and the red vastus lateralis muscles. When the data were expressed as per milligrams of protein, OPR was significantly depressed by diabetes mellitus in the mitochondria from each muscle; a similar negative impact also appeared to be produced by physical training in mitochondria isolated from the red vastus lateralis muscle. However, due to changes in mitochondrial protein yield between groups, the capacity to oxidize pyruvate and malate was also calculated per gram of muscle. Adenosine triphosphate (ATP) production rate appeared to be unaffected by diabetes but significantly increased by training in both muscles of diabetic and nondiabetic rats. This effect of training was not associated with any improvement in plasma glucose or insulin levels in diabetic animals. However, the large increase in plasma levels of beta-hydroxybutyric acid in sedentary diabetic rats was partly reversed by training (1,079 +/- 472 v 3,424 +/- 618 micromol, P < .001). These results suggest that the training-induced increase in the capacity of skeletal muscles to oxidize substrates and generate energy may also contribute to reduce the elevated plasma beta-hydroxybutyric acid levels observed in a state of insulin deficiency. This may have clinical relevance, since ketoacidosis remains a life-threatening event in insulin-dependent diabetic subjects.

3-Hydroxybutyric Acid↗

PubMed2001

X-ray structure of 12-oxophytodienoate reductase 1 provides structural insight into substrate binding and specificity within the family of OYE.

BACKGROUND: 12-Oxophytodienoate reductase (OPR) is a flavin mononucleotide (FMN)-dependent oxidoreductase in plants that belongs to the family of Old Yellow Enzyme (OYE). It was initially characterized as an enzyme involved in the biosynthesis of the plant hormone jasmonic acid, where it catalyzes the reduction of the cyclic fatty acid derivative 9S,13S-12-oxophytodienoate (9S,13S-OPDA) to 1S,2S-3-oxo-2(2'[Z]-pentenyl)-cyclopentane-1-octanoate. Several isozymes of OPR are now known that show different stereoselectivities with regard to the four stereoisomers of OPDA. RESULTS: Here, we report the high-resolution crystal structure of OPR1 from Lycopersicon esculentum and its complex structures with the substrate 9R,13R-OPDA and with polyethylene glycol 400. OPR1 crystallizes as a monomer and folds into a (betaalpha)(8) barrel with an overall structure similar to OYE. The cyclopentenone ring of 9R,13R-OPDA is stacked above the flavin and activated by two hydrogen bonds to His187 and His190. The olefinic bond is properly positioned for hydride transfer from the FMN N(5) and proton transfer from Tyr192 to Cbeta and Calpha, respectively. Comparison of the OPR1 and OYE structures reveals striking differences in the loops responsible for binding 9R,13R-OPDA in OPR1. CONCLUSIONS: Despite extensive biochemical characterization, the physiological function of OYE still remains unknown. The similar catalytic cavity structures and the substrate binding mode in OPR1 strongly support the assumption that alpha,beta-unsaturated carbonyl compounds are physiological substrates of the OYE family. The specific binding of 9R,13R-OPDA by OPR1 explains the experimentally observed stereoselectivity and argues in favor of 9R,13R-OPDA or a structurally related oxylipin as natural substrate of OPR1.

Binding Sites↗

PubMed2001

Isolation and structural characterization of tetra-n-propyl zirconate in hydrocarbon solution and the solid state.

Tetra-n-propyl zirconate has been purified by vacuum distillation and isolated as an extremely moisture sensitive, crystalline solid. According to a single-crystal X-ray diffraction study, crystalline tetra-n-propyl zirconate is composed of tetrameric Zr(4)(OPr(n))(16) (1) molecules whose Zr(4)O(16) metal-oxygen core structure has virtual C(2)(h) symmetry, the same structure observed previously for n-alkyl orthotitanates. Carbon-13 NMR spectroscopic data indicate that this core structure is retained in hydrocarbon solution. Molecule 1 has the same M(4)O(16) metal-oxygen core structure as [CH(3)C(CH(2)O)(3)](2)M(4)(OPr(i))(10), M = Ti, where the metal centers have octahedral coordination geometry, but a metal-oxygen core structure different from that of the M = Zr case, where trigonal metaprismatic coordination geometry is observed.

Carbon↗

PubMed2002

Direct addition of alcohols to organonitriles activated by ligation to a platinum(IV) center.

Treatment of trans-[PtCl(4)(RCN)(2)] (R = Me, Et) with R'OH (R' = Me, Et, n-Pr, i-Pr, n-Bu) at 45 degrees C in all cases allowed the isolation of the trans-[PtCl(4)[(E)-NH=C(R)OR'](2)] imino ester complexes, while the reaction between cis-[PtCl(4)(RCN)(2)] and the least sterically hindered alcohols (methanol and ethanol) results in the formation of cis-[PtCl(4)[(E)-NH=C(R)OR'](2)] (R/R' = Me/Me) or trans-[PtCl(4)[(E)-NH=C(Et)OR'](2)] (R' = Me, Et), the latter being formed via thermal isomerization (ROH, reflux, 3 h) of the initially formed corresponding cis isomers. The reaction between alcohols R'OH and cis-[PtCl(4)(RCN)(2)] (R = Me, R' = Et, n-Pr, i-Pr, n-Bu; R = Et; R' = n-Pr, i-Pr, n-Bu), exhibiting greater R/R' steric congestion, allowed the isolation of cis-[PtCl(4)[(E)-NH=C(R)OR'][(Z)-NH=C(R)OR']] as the major products. The alcoholysis reactions of poorly soluble [PtCl(4)(RCN)(2)] (R = CH(2)Ph, Ph) performed under heterogeneous conditions, directly in the appropriate alcohol and for a prolonged time and, for R = Ph, with heating led to trans-[PtCl(4)[(E)-NH=C(R)OR'](2)] (R = CH(2)Ph, R' = Me, Et, n-Pr, i-Pr; R = Ph, R' = Me) isolated in moderate yields. In all of the cases, in contrast to platinum(II) systems, addition of R'OH to the organonitrile platinum(IV) complexes occurs under mild conditions and does not require a base as a catalyst. The formed isomerically pure (imino ester)Pt(IV) complexes can be reduced selectively, by Ph(3)P=CHCO(2)Me, to the corresponding isomers of (imino ester)Pt(II) species, exhibiting antitumor activity, without change in configuration of the imino ester ligands. Furthemore, the imino esters NH=C(R)OR' can be liberated from both platinum(IV) and platinum(II) complexes [PtCl(n)[H=C(R)OR'](2)] (n = 2, 4) by reaction with 1,2-bis(diphenylphosphino)ethane and pyridine, respectively. All of the prepared compounds were characterized by elemental analyses (C, H, N), FAB mass spectrometry, IR, and (1)H, (13)C[(1)H], and (195)Pt (metal complexes) NMR spectroscopies; the E and Z configurations of the imino ester ligands in solution were determined by observation of the nuclear Overhauser effect. X-ray structure determinations were performed for trans-[PtCl(4)[(E)-NH=C(Me)OEt](2)] (2), trans-[PtCl(4)[(E)-NH=C(Et)OEt](2)] (10), trans-[PtCl(4)[(E)-NH=C(Et)OPr-i](2)] (11), trans-[PtCl(4)[(E)-NH=C(Et)OPr-n](2)] (12), and cis-[PtCl(4)[(E)-NH=C(Et)OMe](2)] (14). Ab initio calculations have shown that the EE isomers are the most stable ones for both platinum(II) and platinum(IV) complexes, whereas the most stable configurations for the ZZ isomers are less stable than the respective EZ isomers, indicating an increase of the stability on moving from the ZZ to the EE configurations which is more pronounced for the Pt(IV) complexes than for the Pt(II) species.

Journal Article↗

PubMed2003

Ligand substitution in cubic clusters: surprising isolation of the cocrystallization products of Cu8(mu8-Se)[S2P(OEt)2]6 and Cu6[S2P(OEt)2]6.

The cluster (Cu8(mu8-Se)[S2P(OEt)2]6)0.54(Cu6[S2P(OEt)2]6)0.46 (2) was prepared in 78% yield from the reaction of Cu8(Se)[Se2P(OPr)2]6 (1) and NH4S2P(OEt)2 in toluene. The central selenide ion in 2 was characterized by 77Se NMR at delta -976 ppm. The simulated solid-state 31P NMR spectrum shows two components with an intensity ratio close to 55:45. The peak centered at 100.7 ppm is assigned to the 31P nuclei in the hexanuclear copper cluster, and that at 101.1 ppm is due to the octanuclear copper cluster. The single-crystal X-ray diffraction analysis confirms the cocrystallization structures of Cu8(Se)[S2P(OEt)2]6 (54%) and Cu6[S2P(OEt)2]6 (46%) (2: trigonal, space group R3, a=21.0139(13) A, c=11.404(3) A, gamma=120 degrees, Z=3). While the octanuclear copper cluster possesses a 3-fold crystallographic axis which pass through the Cu2, Se, and Cu(2A) atoms, the six copper atoms having the S6 point group symmetry in Cu6[S2P(OEt)2]6 form a compressed octahedron. The Cu8(mu8-Se) cubic core in Cu8(mu8-Se)[S2P(OEt)2]6 is larger in size than the metal core in Cu8(mu8-Se)[Se2P(OPr)2]6 (1) although the bite distance of the Se-containing bridging ligand is larger than that of the S ligand. To understand the nature of the structure contraction of the metal core and metal-mu8-Se interaction, molecular orbital calculations have been carried out at the B3LYP level of density functional theory. MO calculations suggest that Cu-mu8-Se interactions are not very strong and a half bond can be formally assigned to each Cu-mu8-Se bond. Moderate Cu...Cu repulsion exists, and it is the bridging ligands that are responsible for the observed Cu...Cu contacts. Hence, the S-ligating copper clusters have greater Cu...Cu separations because each Cu carries more positive charge in the presence of the more electronegative S-containing ligands.

Journal Article↗

PubMed2005

Methyltriskaidecazirconates, molecular forms of zirconia.

Repeated methanolysis of [Zr(3)O](OPr(n)(10) followed by extraction and crystallization from toluene yields material that is X-ray crystallographically indistinguishable from the compound previously formulated as [Zr(13)O(8)](OMe)(36). Elemental analysis and (1)H solution NMR spectroscopy strongly suggest that this material is a mixture of methyltriskaidecazirconates (MTZ) [Zr(13)O(8)](OMe)(x)(OH)(36)(-)(x), x(av) approximately 20, that readily cocrystallize from hydrocarbon solution. These species have the metal-oxygen framework structure reported for [Zr(13)O(8)](OMe)(36), where the 13 zirconium and 32 bridging oxygen atoms comprise a fragment of the fluorite structure adopted by ZrO(2) at elevated temperatures. Ethanolysis of [Zr(3)O](OPr(n)(10) yields its ethyl analogue, [Zr(3)O](OEt)(10). Both trizirconates display temperature-dependent (1)H solution NMR spectra that are interpreted mechanistically in terms of rearrangement mechanisms involving trigonal twists at the octahedral zirconium centers.

Crystallography, X-Ray↗

PubMed1998

Formic Acid Modified Ti(OCHMe(2))(4). Syntheses, Characterization, and X-ray Structures of Ti(4)(&mgr;(4)-O)(&mgr;-O)(OFc)(2)(&mgr;-OR)(4)(OR)(6) and Ti(6)(&mgr;(3)-O)(6)(OFc)(6)(OR)(6) (OFc = O(2)CH; OR = OCHMe(2)).

Novel structural arrangements for carboxylic acid modified titanium alkoxides were obtained from stoichiometric reactions between titanium isopropoxide (Ti(OPr(i))(4)) and formic acid (HOFc). The 1:1 reaction in toluene forms the tetranuclear species Ti(4)O(2)(OFc)(2)(OPr(i))(10), 1. The structure of 1 was solved in the triclinic space group P&onemacr; with a = 13.034(3) Å, b = 13.467(2) Å, c = 13.996(2) Å, alpha = 98.79(1) degrees, beta = 104.68(2) degrees, and gamma = 97.82(2) degrees for Z = 2. The general structure of 1 resembles two face-shared [Ti-O](4) cubes with one set of mirror-related titanium atoms removed. The oxygen atoms are represented by one &mgr;(4)-O, one &mgr;-O, and four &mgr;-OR ligands, with the remaining sites filled by two OFc ligands and six terminal alkoxides. Increasing the stoichiometry to 1:2 (Ti/HOFc) leads to the isolation of Ti(6)O(6)(OFc)(6)(OR)(6), 2. The structure of 2 was solved in the monoclinic space group P2(1)/c with a = 8.968(2) Å, b = 26.520(4) Å, c = 20.046(2) Å, and beta = 93.19(1) degrees for Z = 4. The structure of 2 consists of two offset six-membered [Ti-(&mgr;(3)-O)](3) rings joined through Ti-O bonds. The OFc ligands are arranged externally around the central hexagon-prism, oscillating between the top and bottom rings. Compound 1 adopts a very symmetrical arrangement in solution due to the labile OFc ligands and was found to undergo "aging" by a trans-esterification mechanism, the rate of which is enhanced by heating. Compound 2 maintains its solid-state structure in solution.

Journal Article↗

PubMed2004

Al-isopropoxydiisobutylalane: a study of the effect of solvent on the rate and stereoselectivity of cyclic ketone reduction.

The effect of solvent on the rate and stereoselectivity of cyclic ketone reduction by Al-isopropoxydiisobutylalane (DIBA(i)OPr) has been investigated. In dichloromethane, DIBA(i)OPr behaves as a bulky reducing agent, approaching the carbonyl group along an equatorial trajectory to produce the axial alcohol with >10:1 stereoselectivity. In sharp contrast, reduction in toluene gives the complementary outcome, affording the thermodynamically more stable isomer with >99:1 stereoselectivity.

Journal Article↗

PubMed2000

An Arabidopsis gene induced by wounding functionally homologous to flavoprotein oxidoreductases.

The regulation of genes in response to wounding is mediated in part by the octadecanoids 12-oxo-phytodienoic acid (OPDA), jasmonic acid (JA) and its methyl ester methyl jasmonate (MeJA). We identified, by differential display, an Arabidopsis gene (OPR3) induced after wounding. OPR3 is homologous to members of the flavin mononucleotide (FMN) binding proteins, including the old yellow enzyme (OYE) from yeast and 12-oxophytodienoate-10,11-reductase (OPR) from Arabidopsis. Transcripts of OPR3 rapidly accumulated in leaves after wounding and MeJA treatment, but they were detected in various tissues of unwounded plants at relatively low levels. Expression of the OPR3 gene was significantly reduced in wounded leaves of the coil mutant, indicating partial dependence on jasmonate perception for full induction of the gene. The recombinant protein of OPR3 cross-reacted with an antiserum raised against the OYE protein, and showed oxidation of beta-NADPH when OPDA or 15-deoxy-delta(12,14) prostaglandin J2 (PGJ2), an analogue of OPDA, was used as substrate. Beta-NADPH oxidation was not observed when MeJA, which lacks the double bond in the ketone ring, was used as substrate. The recombinant OPR3 protein also showed beta-NADPH oxidation activity in the presence of cyclohexenone, but not cyclohexanone, suggesting that the enzyme has specificity to cleavage of olefinic bonds in cyclic enones. The results show that the OPR3 gene product represents a new OPR of Arabidopsis induced after wounding.

Acetates↗

PubMed2003

Clinical evaluation of peak endocardial acceleration as a sensor for rate responsive pacing.

An innovative control parameter for rate responsive (RR) pacing that uses a sensor to measure mechanical vibrations generated by the myocardium during the isovolumetric contraction phase (peak endocardial acceleration [PEA]), has been devised by SORIN Biomedica (BEST Living System). To assess the physiological sensitivity of the pacemaker sensor along with reliability of the algorithm to supply appropriate pacing rates three different relationships were examined (linear regression analysis): (1) recorded deltaPEA exercise steps against the calculated energy cost of exercise (MET), (2) exercise pacing rates against predicted values, and (3) deltaPEA against exercise pacing rates. Fifteen patients (mean age 68 +/- 12 years) in NYHA Class I-II, implanted with the BEST Living System (Living 1 DDDR pacemaker) for advanced AVB and/or SSS, underwent one of the following maximal exercise stress protocols: bicycle (25 W, 2-minute steps) or Bruce or Chronotropic Assessment Exercise Protocol (CAEP). Pacing rates for each step were matched against those predicted by a reliable and tested custom software called Pacing Rate Profile Software (PRPS). The PRPS is based on the oxygen pulse reserve (OPR) method (OPR = VO2 reserve divided by heart rate reserve), American College of Sports Medicine (ACSM) formulas for calculating workload/metabolic requirements, and data derived from the Weber functional classes. On the basis of certain patient, data the PRPS then supplies appropriate metabolic pacing rate profiles. In all 15 patients linear regression analysis of deltaPEA against MET, as evaluated during the exercise protocol steps, showed a high correlation (r = 0.97). Likewise, a high correlation was also obtained between PRPS predicted heart rates and exercise pacing rates (r = 0.96) and PEA against exercise pacing rates (r = 0.96). The results of this study show that, through PEA dynamic monitoring, the SORIN Best Living System produces physiological pacing rates that are significantly related to metabolic needs.

Aged↗

PubMed2006

Crystal structure of 12-oxophytodienoate reductase 3 from tomato: self-inhibition by dimerization.

12-Oxophytodienoate reductase (OPR) 3, a homologue of old yellow enzyme (OYE), catalyzes the reduction of 9S,13S-12-oxophytodienoate to the corresponding cyclopentanone, which is subsequently converted to the plant hormone jasmonic acid (JA). JA and JA derivatives, as well as 12-oxophytodienoate and related cyclopentenones, are known to regulate gene expression in plant development and defense. Together with other oxygenated fatty acid derivatives, they form the oxylipin signature in plants, which resembles the pool of prostaglandins in animals. Here, we report the crystal structure of OPR3 from tomato and of two OPR3 mutants. Although the catalytic residues of OPR3 and related OYEs are highly conserved, several characteristic differences can be discerned in the substrate-binding regions, explaining the remarkable substrate stereoselectivity of OPR isozymes. Interestingly, OPR3 crystallized as an extraordinary self-inhibited dimer. Mutagenesis studies and biochemical analysis confirmed a weak dimerization of OPR3 in vitro, which correlated with a loss of enzymatic activity. Based on structural data of OPR3, a putative mechanism for a strong and reversible dimerization of OPR3 in vivo that involves phosphorylation of OPR3 is suggested. This mechanism could contribute to the shaping of the oxylipin signature, which is critical for fine-tuning gene expression in plants.

Amino Acid Sequence↗