scholarly journals Chymotrypsin activates cardiac mitochondrial carnitine-acylcarnitine translocase

1989 ◽  
Vol 261 (2) ◽  
pp. 363-370 ◽  
Author(s):  
P E Wolkowicz ◽  
D F Pauly ◽  
W B Van Winkle ◽  
J B McMillin
Keyword(s):  
Ultrastructural Changes ◽  
Maximal Velocity ◽  
Mitochondrial Matrix ◽  
Beta Oxidation ◽  
Passive Permeability ◽  
Inhibitor Binding ◽  
Maximal Inhibition ◽  
Binding Properties ◽  
Submitochondrial Particle ◽  
Acylcarnitine Translocase

The carnitine-acylcarnitine translocase facilitates carnitine and acylcarnitine transport into the mitochondrial matrix during beta-oxidation. Our results demonstrate that chymotrypsin can activate the maximal velocity of N-ethylmaleimide (NEM)-sensitive carnitine or palmitoylcarnitine exchange 7-fold, while doubling the affinity of the translocase for carnitine. Chymotrypsin activation is strictly dependent on the presence of free or short-chain acylcarnitine in the proteolysis medium, the extent of activation decreasing as the acylcarnitine chain length in the proteolysis medium increases. Chymotrypsin treatment decreases the apparent I50 value (inhibitor concentration required to give half-maximal inhibition) of the translocase for inhibition by NEM only under conditions which produce translocase activation. Modification of submitochondrial particle membranes by chymotrypsin does not result in gross ultrastructural changes or in an increase in the passive permeability of these membranes to carnitine. The data suggest that carnitine binding produces a change in translocase conformation which allows chymotrypsin modification to occur. This modification alters the kinetic and inhibitor-binding properties of the translocase.

scholarly journals Prothioconazole and Prothioconazole-Desthio Activities against Candida albicans Sterol 14-α-Demethylase

2012 ◽  
Vol 79 (5) ◽  
pp. 1639-1645 ◽  
Author(s):  
Josie E. Parker ◽  
Andrew G. S. Warrilow ◽  
Hans J. Cools ◽  
Bart A. Fraaije ◽  
John A. Lucas ◽  
...  
Keyword(s):  
Candida Albicans ◽  
Type Ii ◽  
Inhibitor Binding ◽  
Binding Properties ◽  
Content Type ◽  
Azole Antifungals ◽  
A Cell ◽  
Antifungal Action ◽  
Binding Spectra

ABSTRACTProthioconazole is a new triazolinthione fungicide used in agriculture. We have usedCandida albicansCYP51 (CaCYP51) to investigate thein vitroactivity of prothioconazole and to consider the use of such compounds in the medical arena. Treatment ofC. albicanscells with prothioconazole, prothioconazole-desthio, and voriconazole resulted in CYP51 inhibition, as evidenced by the accumulation of 14α-methylated sterol substrates (lanosterol and eburicol) and the depletion of ergosterol. We then compared the inhibitor binding properties of prothioconazole, prothioconazole-desthio, and voriconazole with CaCYP51. We observed that prothioconazole-desthio and voriconazole bind noncompetitively to CaCYP51 in the expected manner of azole antifungals (with type II inhibitors binding to heme as the sixth ligand), while prothioconazole binds competitively and does not exhibit classic inhibitor binding spectra. Inhibition of CaCYP51 activity in a cell-free assay demonstrated that prothioconazole-desthio is active, whereas prothioconazole does not inhibit CYP51 activity. Extracts fromC. albicansgrown in the presence of prothioconazole were found to contain prothioconazole-desthio. We conclude that the antifungal action of prothioconazole can be attributed to prothioconazole-desthio.

Ultrastructural changes induced in zoospores of Lagenidium callinectes by exposure to Captan

1979 ◽  
Vol 57 (20) ◽  
pp. 2116-2121 ◽  
Author(s):  
D. G. Ruch ◽  
C. E. Bland
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Fine Structure ◽  
Nuclear Matrix ◽  
Active Component ◽  
Marine Fungus ◽  
Toxic Action ◽  
Ultrastructural Changes ◽  
Mitochondrial Matrix ◽  
Growth Development

The effects of the fungicide Captan on growth, development, and fine structure of the marine fungus Lagenidium callinectes Couch are studied. At the minimum lethal concentration (LC100) of Captan for L. callinectes (3.2 ppm active component), zoospores exposed for 30 min failed to encyst or germinate. Ultrastructural changes caused by exposure to Captan included "washing-out" of the mitochondrial matrix and disappearance of many of the cristae, clumping of the chromatin and disappearance of the nuclear matrix, and swelling of the cisternae of the endoplasmic reticulum. Longer exposure of zoospores to Captan resulted ultimately in breakdown of the plasma membrane. These observations were in agreement with those of previous studies which indicated that the toxic action of Captan occurs primarily in mitochondria.

Bupivacaine Inhibits Acylcarnitine Exchange in Cardiac Mitochondria

2000 ◽  
Vol 92 (2) ◽  
pp. 523-523 ◽  
Author(s):  
Guy L. Weinberg ◽  
June W. Palmer ◽  
Timothy R. VadeBoncouer ◽  
Mikko B. Zuechner ◽  
Guy Edelman ◽  
...  
Keyword(s):  
Local Anesthetics ◽  
Adenosine Diphosphate ◽  
Carnitine Deficiency ◽  
Cardiac Mitochondria ◽  
Beta Oxidation ◽  
Pyruvate Oxidation ◽  
Interfibrillar Mitochondria ◽  
Carnitine Metabolism ◽  
Acylcarnitine Translocase ◽  
Fatty Acid Beta Oxidation

Background The authors previously reported that secondary carnitine deficiency may sensitize the heart to bupivacaine-induced arrhythmias. In this study, the authors tested whether bupivacaine inhibits carnitine metabolism in cardiac mitochondria. Methods Rat cardiac interfibrillar mitochondria were prepared using a differential centrifugation technique. Rates of adenosine diphosphate-stimulated (state III) and adenosine diphosphate-limited (state IV) oxygen consumption were measured using a Clark electrode, using lipid or nonlipid substrates with varying concentrations of a local anesthetic. Results State III respiration supported by the nonlipid substrate pyruvate (plus malate) is minimally affected by bupivacaine concentrations up to 2 mM. Lower concentrations of bupivacaine inhibited respiration when the available substrates were palmitoylcarnitine or acetylcarnitine; bupivacaine concentration causing 50% reduction in respiration (IC50 +/- SD) was 0.78+/-0.17 mM and 0.37+/-0.03 mM for palmitoylcarnitine and acetylcarnitine, respectively. Respiration was equally inhibited by bupivacaine when the substrates were palmitoylcarnitine alone, or palmitoyl-CoA plus carnitine. Bupivacaine (IC50 = 0.26+/-0.06 mM) and etidocaine (IC50 = 0.30+/-0.12 mM) inhibit carnitine-stimulated pyruvate oxidation similarly, whereas the lidocaine IC50 is greater by a factor of roughly 5, (IC50 = 1.4+/-0.26 mM), and ropivacaine is intermediate, IC50 = 0.5+/-0.28 mM. Conclusions Bupivacaine inhibits mitochondrial state III respiration when acylcarnitines are the available substrate. The substrate specificity of this effect rules out bupivacaine inhibition of carnitine palmitoyl transferases I and II, carnitine acetyltransferase, and fatty acid beta-oxidation. The authors hypothesize that differential inhibition of carnitine-stimulated pyruvate oxidation by various local anesthetics supports the clinical relevance of inhibition of carnitine-acylcarnitine translocase by local anesthetics with a cardiotoxic profile.

The Na+/H+ antiport in renal mitochondria

1995 ◽  
Vol 268 (5) ◽  
pp. C1227-C1234 ◽  
Author(s):  
M. Sastrasinh ◽  
P. Young ◽  
E. J. Cragoe ◽  
S. Sastrasinh
Keyword(s):  
Direct Interaction ◽  
Maximal Velocity ◽  
Mitochondrial Matrix ◽  
Na Transport ◽  
Submitochondrial Particles ◽  
Saturation Kinetics ◽  
Na Efflux ◽  
Amiloride Derivatives ◽  
Menten Constant ◽  
Na Uptake

In isolated renal mitochondria, Na+ and Li+ stimulated H+ efflux from the mitochondrial matrix. In submitochondrial particles (SMP), Na+ flux was also coupled to H+ transport in the opposite direction. The overshoot of Na+ uptake in SMP with an outwardly directed H+ gradient indicated that downhill efflux of H+ through the mitochondrial membrane induced uphill transport of Na+. Similar to the Na+/H+ antiport in other types of mitochondria, the antiport in renal mitochondria was more sensitive to amiloride derivatives than to amiloride itself. Benzamil and ethylisopropylamiloride (EIPA), but not amiloride, inhibited the antiport, with 50% inhibition of 10(-4) M for both benzamil in mitochondria and EIPA in SMP. The Na+/H+ antiport in renal mitochondria had simple saturation kinetics for external Na+ [Michaelis-Menten constant (Km) = 3.27 +/- 0.63 mM; maximal velocity (Vmax) = 0.022 +/- 0.002 pH units/s] and Li+ (Km = 3.62 +/- 0.75 mM; Vmax = 0.022 +/- 0.002 pH units/s). NH4Cl and NH4 acetate stimulated Na+ efflux and inhibited Na+ uptake in SMP. Comparable results with NH4 acetate and chloride suggested that NH4+ modified Na+ transport through its direct interaction with the Na+/H+ antiport, rather than through the alkalinization of intra-SMP space from non-ionic diffusion of NH3. These results suggested that the Na+/H+ antiport may be a factor in the exit of NH4+ from renal mitochondria.

scholarly journals Crystal structures and inhibitor binding properties of plant class V chitinases: the cycad enzyme exhibits unique structural and functional features

2015 ◽  
Vol 82 (1) ◽  
pp. 54-66 ◽  
Author(s):  
Naoyuki Umemoto ◽  
Yuka Kanda ◽  
Takayuki Ohnuma ◽  
Takuo Osawa ◽  
Tomoyuki Numata ◽  
...  
Keyword(s):  
Crystal Structures ◽  
Inhibitor Binding ◽  
Binding Properties ◽  
Class V ◽  
Functional Features

Inhibition of mitochondrial carnitine–acylcarnitine translocase by sulfobetaines

1980 ◽  
Vol 58 (10) ◽  
pp. 822-830 ◽  
Author(s):  
Rehana Parvin ◽  
Tapas Goswami ◽  
Shri V. Pande
Keyword(s):  
Rat Heart ◽  
Liver Mitochondria ◽  
Inhibitory Effect ◽  
Carnitine Acetyltransferase ◽  
Selective Inhibitors ◽  
Maximal Inhibition ◽  
Isolation Medium ◽  
Carnitine Acyltransferases ◽  
Rat Heart Mitochondria ◽  
Acylcarnitine Translocase

Sulfobetaines (N-alkyl-N,N-dimethyl-3-ammonio-1-propanesulfonates) have been identified as relatively specific and selective inhibitors of mitochondrial carnitine–acylcarnitine translocase. Thus, sublytic concentrations of sulfobetaines (alkyl = octyl to tetradecyl) inhibit the respiration of rat heart mitochondria supported by added acylcarnitines or pyruvate plus malonate and carnitine. Both exchange efflux and unidirectional net efflux of mitochondrial carnitine are also inhibited; the half-maximal inhibition of the former occurs at micromolar concentrations of sulfobetaines and the inhibitory effect is reversible and competitive with respect to carnitine. As a stop-inhibitor, 20 mM sulfobetaine8, (alkyl = octyl), is useable at near 0 °C but is less effective than 2 mM mersalyl when transport rates are very rapid as at higher temperatures especially with liver mitochondria. The loss of mitochondrial carnitine that normally occurs owing to the progress of net efflux during the isolation of mitochondria is prevented by the inclusion of 20 mM sulfobetaine8 in the isolation medium and this enables a better estimate of the mitochondrial carnitine content. Sulfobetaines inhibit the activities of mitochondrial carnitine acetyltransferase and carnitine palmitoyltransferase but only at concentrations severalfold higher than those inhibitory for the translocase. This observation supports the belief that carnitine–acylcarnitine translocase is an entity distinct from that of carnitine acyltransferases.

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