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1.
Increased ATP/ADP ratio resulting from enhanced glycolysis and oxidative phosphorylation represents a plausible mechanism controlling the glucose-stimulated insulin secretion (GSIS) in pancreatic β-cells. Although specific bioenergetics might be involved, parallel studies of cell respiration and mitochondrial membrane potential (Δ Ψm) during GSIS are lacking. Using high resolution respirometry and parallel Δ Ψm monitoring by two distinct fluorescence probes we have quantified bioenergetics in rat insulinoma INS-1E cells representing a suitable model to study in vitro insulin secretion. Upon glucose addition to glucose-depleted cells we demonstrated a simultaneous increase in respiration and Δ Ψm during GSIS and showed that the endogenous state 3/state 4 respiratory ratio hyperbolically increased with glucose, approaching the maximum oxidative phosphorylation rate at maximum GSIS. Attempting to assess the basis of the “toxic” effect of fatty acids on insulin secretion, GSIS was studied after linoleic acid addition, which diminished respiration increase, Δ Ψm jump, and magnitude of insulin release, and reduced state 3/state 4 dependencies on glucose. Its effects were due to protonophoric function, i.e. uncoupling, since without glucose, linoleic acid accelerated both state 3 and state 4 respiration by similar extent. In turn, state 3 respiration increased marginally with linoleic acid at 10–20 mM glucose. We conclude that upon glucose addition in physiological range, the INS-1E cells are able to regulate the oxidative phosphorylation rate from nearly zero to maximum and that the impairment of GSIS by linoleic acid is caused by mitochondrial uncoupling. These findings may be relevant to the pathogenesis of type 2 diabetes. 相似文献
2.
The cytotoxicity and its underlying mechanisms induced by gliotoxin (GT), an immunosuppressive agent, in macrophages are poorly understood. We report here that GT induced a rapid apoptosis (DNA fragmentation and hypodiploid nuclei obtained within 4 hrs of treatment) in murine macrophages PU5-1.8 in a dose-dependent and cell cycle-independent manner. The GT-induced apoptosis was suppressed by z-Asp, z-VAD-fmk and antioxidants suggesting that production of reactive oxygen species (ROS) and activation of caspases were important in this process. Also, release of cytochrome c from mitochondria was found to be an early event (within 1 hr) after addition of GT (250 ng/ml) and its presence in the cytosol was sufficient to elicit apoptosis. Interestingly, the release of cytochrome c was not accompanied by a reduction in the mitochondrial membrane potential ( ψm) as determined by several ψm-sensitive fluorescent indicators. Taken together, our results indicate that GT is a potent apoptotic agent in PU5-1.8 cells and the loss of ψm is not a universal early marker for apoptosis. 相似文献
3.
1. 1. By varying the redox potential of a chloroplast suspension, we obtained new evidence for an equilibrium between states S0 and S1 in the model of Kok, B., Forbush, B. and McGloin, N. (1970, Photochem. Photobiol. 11, 457–475). The mid-point potential of the S0 to S1 couple is close to that for the pool of the electron acceptor of System II, A to A−. 2. 2. The limiting steps between two consecutive photoreactions of System II in Chlorella and spinach chloroplasts, have been studied. 2.1. (a) The limiting step from S1 to S2 (noted γ1 (Δt)) is not exponential. Its temperature coefficient becomes greater as the reaction proceeds. The shape of the kinetics is an intrinsic property of each center. Chloroplasts fixed with 2% glutaraldehyde, show simple first order kinetics. 2.2. (b) The limiting step from S0 to S1 (γ0 (Δt)) exhibits the same characteristics as γ1 (Δt)). 2.3. (c) The limiting step from S2 to S3 (γ2 (Δt)) shows sigmoidal kinetics; two reactions are involved. One of the reactions exhibits the same properties as γ0 (Δt) and γ1 (Δt). 2.4. (d) The limiting step from S3 to S0 (γ3 (Δt)) is a first order reaction, two times slower than the other transitions. This reaction is interpretated in terms of oxygen release.
3. 3. We also studied the limiting steps in the presence of low concentrations (50 μM) of hydroxylamine. The results favor the binding of two molecules of hydroxylamine to every photochemical center.
Abbreviations: DCIP, dichlorophenolindophenol 相似文献
4.
The effects of inorganic phosphate (P i), the main intracellular membrane permeable anion capable of altering mitochondrial pH gradients (ΔpH), were measured on mitochondrial H 2O 2 release. As expected, P i decreased ΔpH and increased the electric membrane potential (ΔΨ). Mitochondrial H 2O 2 release was stimulated by P i and also by its structural analogue arsenate. However, acetate, another membrane-permeable anion, did not stimulate mitochondrial H 2O 2 release. The stimulatory effect promoted by P i was prevented by CCCP, which decreases transport of P i across the inner mitochondrial membrane, indicating that P i must be in the mitochondrial matrix to stimulate H 2O 2 release. In conclusion, we found that P i and arsenate stimulate mitochondrial reactive oxygen release, an effect that may contribute towards oxidative stress under conditions such as ischemia/reperfusion, in which high-energy phosphate bonds are hydrolyzed. 相似文献
5.
The effects of forskolin on electrical coupling among pancreatic β-cells were studied. Two microelectrodes were used to measure membrane potentials simultaneously in pairs of islet β-cells. Intracellular injection of a current pulse ( ΔI) elicited a membrane response ΔV1 in the injected cell and also a response ΔV2 in a nearby β-cell confirming the existence of cell-to-cell electrical coupling among islet β-cells. In the presence of glucose (7 mM), application of forskolin evoked a transient depolarization of the membrane and electrical activity suggesting that the drug induced a partial inhibition of the β-cell membrane K + conductance. Concomitant with this depolarization of the membrane there was a marked decrease in β-cell input resistance ( ΔV2/ ΔI) suggesting that exposure to forskolin enhanced intercellular coupling. Direct measurements of the coupling ratio ΔV2/ ΔV1 provided further support to the idea that forskolin enhances electrical coupling among islet cells. Indeed, application of forskolin reversibly increased the coupling ratio. These results suggest that cAMP might be involved in the modulation of electrical coupling among islet β-cells. 相似文献
6.
The aim of this study was to examine the protection of the yeast lacking the “antioxidant-like” prion precursor protein (Ure2p), by antioxidants and to elucidate how modification of redox homeostasis affects toxicity of agents inducing oxidative stress in the Δure2 cells. We found a diverse ability of a range of antioxidants to ameliorate the hypersensitivity of the Δure2 disruptant to oxidants and heavy metal ions. Glutathione and then ascorbate were the most effective antioxidants; Tempol, Trolox and melatonin were much less effective or even hampered the growth of the Δure2 cells exposed to tested agents. The intracellular level of ROS was augmented in the Δure2 mutant under normal growth conditions (1.7-fold), and after treatment with H 2O 2 (2.3-fold) and Cd(II) (2.8-fold), with respect to its wild-type counterpart. Glutathione was unable to prevent the increase in ROS production caused by CdCl 2. The Δure2 disruptant was also hypersensitive to heat shock, like mutants lacking glutathione S-transferases. 相似文献
7.
The spectral and metabolic properties of Rhodamine 123, a fluorescent cationic dye used to label mitochondria in living cells, were investigated in suspensions of isolated rat-liver mitochondria. A red shift of Rhodamine 123 absorbance and fluorescence occurred following mitochondrial energization. Fluorescence quenching of as much as 75% also occurred. The red shift and quenching varied linearly with the potassium diffusion potential, but did not respond to ΔpH. These energy-linked changes were accompanied by dye uptake into the matrix space. Concentration ratios, in-to-out, approached 4000:1. A large fraction of internalized dye was bound. At concentrations higher than those needed to record these spectral changes, Rhodamine 123 inhibited ADP-stimulated (State 3) respiration of mitochondria ( Ki = 12 μM) and ATPase activity of inverted inner membrane vesicles ( Ki = 126 μM) and partially purified F 1-ATPase ( Ki = 177 μM). The smaller Ki for coupled mitochondria was accounted for by energy-dependent Rhodamine 123 uptake into the matrix. Above about 20 nmol/mg protein (10 μM), Rhodamine 123 caused rapid swelling of energized mitochondria. Effects on electron-transfer reactions and coupling were small or negligible even at the highest Rhodamine 123 concentrations employed. Δψ-dependent Rhodamine 123 uptake together with Rhodamine 123 binding account for the intense fluorescent staining of mitochondria in living cells. Inhibition of mitochondria ATPase likely accounts for the cytotoxicity of Rhodamine 123. At concentrations which do not inhibit mitochondrial function, Rhodamine 123 is a sensitive and specific probe of Δψ in isolated mitochondria. 相似文献
8.
The lipophilic triphenylmethylphosphonium cation (TPMP +) has been employed to measure ΔΨ m, the electrical potential across the inner membrane of the mitochondria of intact hepatocytes. The present studies have examined the validity of this technique in hepatocytes exposed to graded concentrations of inhibitors of mitochondrial energy transduction. Under these conditions, TPMP + uptake allows a reliable measure of ΔΨ m in intracellular mitochondria, provided that the ratio [TPMP +] i/[TPMP +] e is greater than 50:1 and that at the end of the incubation more than 80% of the hepatocytes exclude Trypan blue. Hepatocytes, staining with Trypan blue, incubated in the presence of Ca 2+, do not concentrate TPMP +. The relationships between ΔΨ m and two other indicators of cellular energy state, Δ GPc and Eh, or between ΔΨ m and J0, were examined in hepatocytes from fasted rats by titration with graded concentrations of inhibitors of mitochondrial energy transduction. Linear relationships were generally observed between ΔΨ m and Δ GPc, Eh or J0 over the ΔΨ m range of 120−160 mV, except in the presence of carboxyatractyloside or oligomycin, where ΔΨ m remained constant. Both the magnitude and the direction of the slope of the observed relationships depended upon the nature of the inhibitor. Hepatocytes from fasted rats synthesized glucose from lactate or fructose, and urea from ammonia, at rates which were generally linear functions of the magnitude of ΔΨ m, except in the presence of oligomycin or carboxyatractyloside. Linear relationships were also observed between ΔΨ m and the rate of formation of lactate in cells incubated with fructose and in hepatocytes from fed rats. The linear property of these force-flow relationships is taken as evidence for the operation of thermodynamic regulatory mechanisms within hepatocytes. 相似文献
9.
Enzymic aromatization of Δ 6- and Δ 1,6-derivatives of the natural substrate androstenedione with human placental aromatase was first studied using gas-chromatography-mass spectrometry. The two steroids were aromatized with apparent Km and Vmax values of 62 nM and 32 pmol/min/mg protein for the Δ 6-steroid and 167 nM and 10 pmol/min/mg protein for the Δ 1,6-steroid, respectively. We next explored the aromatization of a series of 6-alkyl (methyl, ethyl, n-propyl, and n-pentyl)-substituted Δ 6-androstenediones and their Δ 1,6-analogs, potent competitive inhibitors of aromatase, to gain insight into the relationships between the inhibitory activity of the 6-alkyl-C 19 steroids and their ability to serve as a substrate of aromatase. In a series of the Δ 1,6-androstenediones, all the 6-alkyl steroids were more efficient substrates than the parent Δ 1,6-steroid in which the aromatization rates of the alkyl steroids were about 2-fold that of the parent steroid, in contrast, all of the 6-alkyl-substituted Δ 6-androstenediones were converted into the corresponding 6-alkyl-Δ 6-estrogens with the rates of less than about a half that of the parent steroid. These results indicate that the 6-alkyl function decreases the aromatization rate of the Δ 6-steroid but enhances that of the Δ 1,6-steroid. The relative apparent Km values for the C 19 steroids obtained in this study are different from the relative Ki values obtained previously, indicating that a good inhibitor is not essentially a good substrate in the 6-alkyl-substituted Δ 6- and Δ 1,6-androstenedione series. 相似文献
10.
The distribution of glutamate and aspartate and the mitochondrial membrane potential (Δψ) were studied in isolated rat heart mitochondria and in the intact perfused rat heart. The diffusion potential imposed by the glutamate-aspartate exchange through mediation of the electrogenic glutamate-aspartate translocator attained a value close to the mitochondrial Δψ measured from the distribution of triphenylmethylphosphonium ion (TPMP +) both in isolated mitochondria and in intact myocardium. Distributions of the Δψ probe and metabolites were determined by subcellular fractionation of the heart muscle in a non-aqueous medium. The results indicate that the glutamate-aspartate translocator is in near equilibrium in the myocardium. The diffusion potential of the glutamate-aspartate exchange, and the mitochondrial/cytosolic difference in the redox potentials of the free NAD +/NADH pools are equal allowing for experimental error. These data obtained from intact tissue can therefore be interpreted as supporting the notion of the transmembrane uphill transport of reducing equivalent from the cytosolic free NAD +/NADH pool being driven by the malate-aspartate cycle energized by the mitochondrial Δψ. 相似文献
11.
The relationship between the respiration rate and the magnitude of the electrochemical proton potential (Δμ H+) in rat liver mitochondria was investigated. (1) Under the active-state conditions, the action of inhibitors of either phosphorylation (oligomycin) or respiration (rotenone, malonate) on the respiration and Δμ H+ was measured. Both inhibitors diminished the respiration, whereas rotenone resulted in a decrease of Δμ H+, and oligomycin produced an increase of this potential. The effect of the inhibitors was much more pronounced on the respiration rate than on Δμ H+; for example, the excess of oligomycin produced a 90% inhibition of the respiration while Δμ H+ was changed only by 9%. (2) Under the resting-state conditions, small concentrations of the uncoupler stimulated the respiration while changing Δμ H+ to a relatively small extent. The uncoupler concentrations which doubled and tripled the respiration rate produced only 5 and 9% decrease of Δμ H+, respectively. (3) The present results enabled us to propose a model describing the interrelationship between respiration and Δμ H+. 相似文献
12.
Yeast cytochrome c peroxidase (CCP) efficiently catalyzes the reduction of H 2O 2 to H 2O by ferrocytochrome c in vitro. The physiological function of CCP, a heme peroxidase that is targeted to the mitochondrial intermembrane space of Saccharomyces cerevisiae, is not known. CCP1-null-mutant cells in the W303-1B genetic background ( ccp1Δ) grew as well as wild-type cells with glucose, ethanol, glycerol or lactate as carbon sources but with a shorter initial doubling time. Monitoring growth over 10 days demonstrated that CCP1 does not enhance mitochondrial function in unstressed cells. No role for CCP1 was apparent in cells exposed to heat stress under aerobic or anaerobic conditions. However, the detoxification function of CCP protected respiring mitochondria when cells were challenged with H 2O 2. Transformation of ccp1Δ with ccp1W191F, which encodes the CCP W191F mutant enzyme lacking CCP activity, significantly increased the sensitivity to H 2O 2 of exponential-phase fermenting cells. In contrast, stationary-phase (7-day) ccp1Δ- ccp1W191F exhibited wild-type tolerance to H 2O 2, which exceeded that of ccp1Δ. Challenge with H 2O 2 caused increased CCP, superoxide dismutase and catalase antioxidant enzyme activities (but not glutathione reductase activity) in exponentially growing cells and decreased antioxidant activities in stationary-phase cells. Although unstressed stationary-phase ccp1Δ exhibited the highest catalase and glutathione reductase activities, a greater loss of these antioxidant activities was observed on H 2O 2 exposure in ccp1Δ than in ccp1Δ- ccp1W191F and wild-type cells. The phenotypic differences reported here between the ccp1Δ and ccp1Δ- ccp1W191F strains lacking CCP activity provide strong evidence that CCP has separate antioxidant and signaling functions in yeast. 相似文献
13.
1. The conditions under which mitochondria might catalyse a net reversal of oxidative phosphorylation are analysed. 2. Rat-liver mitochondria, incubated under such conditions, show a strongly diminished affinity for oxygen. 3. The velocity of respiration under these conditions is a hyperbolic function of the oxygen concentration. 4. The Km for oxygen is less than 0.1 μM at low phosphate potential, irrespective of substrate, and 1–3 μM under reversal conditions. 5. The observed kinetics can be accounted for in a simple mechanism for cytochrome oxidase action. 相似文献
14.
We have previously shown that crystals of calcium oxalate (COM) elicit a superoxide (O 2−) response from mitochondria. We have now investigated: (i) if other microparticles can elicit the same response, (ii) if processing of crystals is involved, and (iii) at what level of mitochondrial function oxalate acts. O 2− was measured in digitonin-permeabilized MDCK cells by lucigenin (10 μM) chemiluminescence. [ 14C]-COM dissociation was examined with or without EDTA and employing alternative chelators. Whereas mitochondrial O 2− in COM-treated cells was three- to fourfold enhanced compared to controls, other particulates (uric acid, zymosan, and latex beads) either did not increase O 2− or were much less effective (hydroxyapatite +50%, p < 0.01), with all at 28 μg/cm 2. Free oxalate (750 μM), at the level released from COM with EDTA (1 mM), increased O 2− (+50%, p < 0.01). Omitting EDTA abrogated this signal, which was restored completely by EGTA and partially by ascorbate, but not by desferrioxamine or citrate. Omission of phosphate abrogated O 2−, implicating phosphate-dependent mitochondrial dicarboxylate transport. COM caused a time-related increase in the mitochondrial membrane potential (Δψ m) measured using TMRM fluorescence and confocal microscopy. Application of COM to Fura 2-loaded cells induced rapid, large-amplitude cytosolic Ca 2+ transients, which were inhibited by thapsigargin, indicating that COM induces release of Ca 2+ from internal stores. Thus, COM-induced mitochondrial O 2− requires the release of free oxalate and contributes to a synergistic response. Intracellular dissociation of COM and the mitochondrial dicarboxylate transporter are important in O 2− production, which is probably regulated by Δψ m. 相似文献
15.
A new quinone compound, p-hydroxymethoxybenzobijuglone (HMBBJ), isolated from Juglans mandshurica by bioassay-guided fractionation, showed cytotoxic activity against HeLa cell line. Its chemical structure was determined by NMR and HREIMS spectra. In this paper, its ability to induce apoptosis in HeLa cells was studied for the first time. After treated with HMBBJ, the growth of HeLa cells was inhibited and cells displayed typical morphological apoptotic characteristics. Data from flow cytometry analysis showed that the HeLa cell cycle was arrested in the G2/M phase by HMBBJ, and the apoptotic rate of HeLa cells increased in a dose-dependent manner. Meanwhile, HMBBJ increased the expression of caspase-8, -3 and Bax, decreased the expression of Bcl-2, and lowered the Δ Ψm. These findings reveal that HMBBJ could efficiently induce HeLa cells apoptosis through mitochondria dependent pathway and activation of the caspase cascade, and it may be a potential chemotherapeutic candidate for the treatment of cancer. 相似文献
16.
为了探明典型荒漠灌木优势物种黑沙蒿(俗名油蒿, Artemisia ordosica)光合过程能量中分配对环境波动的相对变化及其长期调节机制, 该研究于2018年4-10月在宁夏盐池毛乌素沙地, 同时使用MONITORING-PAM多通道荧光监测仪和LI-6400XT便携式光合测量仪对黑沙蒿叶片的最小荧光产量( Fo)、最大荧光产量( Fm)、稳态荧光产量( Fs)、光下最大荧光产量( Fm′)、净光合速率( Pn)、暗呼吸速率( Rd)、蒸腾速率( E)和叶片气孔导度( gs)进行现场测定, 在实验室内计算比叶面积( SLA)、单位面积氮含量( Narea)、叶绿素含量( CChl)和叶绿素a/b (Chl a/b), 分析黑沙蒿光合过程能量分配中固碳耗能占比( ΦA)、光呼吸耗能占比( ΦPR)、调节性热耗散耗能占比( ΦNPQ)和非调节性热耗散耗能占比( ΦNO)与环境参数和叶性状参数之间的关系以及能量分配各组分之间的相对变化。结果表明, 光化学反应组分( ΦA、 ΦPR)和热耗散组分( ΦNPQ、 ΦNO)之间呈负相关竞争关系, 两组分内部呈正相关协同关系, E和 ΦA、 ΦPR正相关, 和 ΦNPQ、 ΦNO负相关。在低土壤含水量( SWC)和高饱和水汽压差( VPD)环境条件下, 黑沙蒿 ΦA、 ΦPR和 SLA显著降低, ΦNPQ和 ΦNO显著增加。研究认为, 在长期干旱或高蒸散条件下, 黑沙蒿通过降低 SLA等途径避免水分的过度流失, 同时将部分过剩光能由光呼吸代谢途径转移到热耗散组分进行耗散。波动环境下黑沙蒿形态性状的变异和光合过程能量分配的长期调节机制, 反映了其利用形态与生理的协同可塑性对逆境的适应。 相似文献
17.
A new class of inhibitors of juvenile hormone epoxide hydrolase (JHEH) of Manduca sexta and further in vitro characterization of the enzyme are reported. The compounds are based on urea and amide pharmacophores that were previously demonstrated as effective inhibitors of mammalian soluble and microsomal epoxide hydrolases. The best inhibitors against JHEH activity so far within this class are N-[(Z)-9-octadecenyl]-N′-propylurea and N-hexadecyl-N′-propylurea, which inhibited hydrolysis of a surrogate substrate ( t-DPPO) with an IC 50 around 90 nM. The importance of substitution number and type was investigated and results indicated that N, N′-disubstitution with asymmetric alkyl groups was favored. Potencies of pharmacophores decreased as follows: amide>urea>carbamate>carbodiimide>thiourea and thiocarbamate for N, N′-disubstituted compounds with symmetric substituents, and urea>amide>carbamate for compounds with asymmetric N, N′-substituents. JHEH hydrolyzes t-DPPO with a Km of 65.6 μM and a Vmax of 59 nmol min −1 mg −1 and has a substantially lower Km of 3.6 μM and higher Vmax of 322 nmol min −1 mg −1 for JH III. Although none of these compounds were potent inhibitors of hydrolysis of JH III by JHEH, they are the first leads toward inhibitors of JHEH that are not potentially subject to metabolism through epoxide degradation. 相似文献
18.
Efficacy of several antioxidants in the protection of the yeast Saccharomyces cerevisiae mutants deficient in CuZnSOD and deficient in glutaredoxin 5 to growth restriction induced by oxidants was studied. Ascorbate and glutathione protected the Δsod1 and Δgrx5 mutants against the effects of t-butyl hydroperoxide and cumene hydroperoxide, Δsod1 mutants against oxytetracycline and Δgrx5 mutants against menadione and 2,2'-azobis-(2-amidinopropane). However, Tempol, Trolox and melatonin were much less effective, showing prooxidative effects and, at high concentrations, hampering the growth of the mutants in the absence of exogenous oxidants. These results point to a complication of cellular effects of antioxidants by their prooxidative effects and to the usefulness of cellular tests to evaluate the biological effectiveness of antioxidants. 相似文献
19.
Differential scanning calorimetry, circular dichroism, and visible absorption spectrophotometry were employed to elucidate the structural stability of thermophilic phycocyanin derived from Cyanidium caldarium, a eucaryotic organism which contains a nucleus, grown in acidic conditions (pH 3.4) at 54°C. The obtained results were compared with those previously reported for thermophilic phycocyanin derived from Synechococcus lividus, a procaryote containing no organized nucleus, grown in alkaline conditions (pH 8.5) at 52°C. The temperature of thermal unfolding ( td) was found to be comparable between C. caldarium (73°C) and S. lividus (74°C) phycocyanins. The apparent free energy of unfolding (Δ G[urea]=0) at zero denaturant (urea) concentration was also comparable: 9.1 and 8.7 kcal/mole for unfolding the chromophore part of the protein, and 5.0 and 4.3 kcal/mole for unfolding the apoprotein part of the protein, respectively. These values of td and Δ G[urea]=0 were significantly higher than those previously reported for mesophilic Phormidium luridum phycocyanin (grown at 25°C). These findings revealed that relatively higher values of td and Δ G[urea]=0 were characteristics of thermophilic proteins. In contrast, the enthalpies of completed unfolding (Δ Hd) and the half-completed unfolding (Δ Hd)1/2 for C. caldarium phycocyanin were much lower than those for S. lividus protein (89 versus 180 kcal/mole and 62 versus 115 kcal/mole, respectively). Factors contributing to a lower Δ Hd in C. caldarium protein and the role of charged groups in enhancing the stability of thermophilic proteins were discusse. 相似文献
20.
The glycolytic reaction of grapefruit PPi-dependent phosphofructokinase (PFP) depends on the presence of Fru-2,6-P 2 ( Ka=6.7 nM). This molecule was further demonstrated in grapefruit juice sac cells. Citrate, -ketoglutarate and isocitrate competitively inhibited the binding of Fru-2,6-P 2 to PFP. The affinity for Fru-6-P ( Km=159 μM) and PPi ( Km=33 μM) were not affected by the addition of these molecules. In the gluconeogenic reaction, the presence of Fru-2,6-P 2 did not affect the Km of Fru-1,6-P 2 (61 μM) in contrast to orange fruit PFP. These results led to the building of a computer model of PFP, based on the known structure of Bacillus stearothermophilus ATP-dependent phosphofructokinase (ATP-PFK). The results show that catalysis of Fru-6-P in the chain is most unlikely, due to amino-acid substitutions and that Fru-2,6-P 2 can bind between the and β subunits. 相似文献
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