Peroxidative activity of hemepeptides from horse heart cytochromec

Résumé L'hémoundécapeptide (HUP) a été préparé par digestion pepsique du cytochromec qui a été extrait et purifié à partir du cur de cheval. L'hémooctapeptide (HOP) a été obtenu par digestion trypsique de l'HUP. L'un et l'autre ont donné des produits homogènes par chromatographie sur colonne et sur papier, par électrophorèse sur papier à différents pH et par analyse des acides aminés. On a effectué une analyse spectrométrique de HUP et HOP et déterminé leur activité peroxydasique dans diverses conditions. Ces 2 composés n'ont pas montré d'activité catalasique.

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This paper is based on a thesis submitted byY. Y. Hsiao in partial fulfillment for the degree of Master of Science at Utah State University.     

Permeability of rat heart myocytes to cytochrome c

Rat heart myocytes undergoing progressive damage demonstrate morphological changes of shortening and swelling followed by the formation of intracellular vacuoles and plasma membrane blebbing. The damaged myocytes displayed impaired N,N'-tetramethyl-p-phenyldiamine (TMPD) ascorbate-stimulated respiratory activity which was restored by the addition of reduced cytochrome c to the cell culture medium. To clarify the role played by cytochrome c in the impairment of cell respiration, polarographic, spectrophotometric and fluorescence as well as electron microscopy imaging experiments were performed. TMPD/ascorbate-stimulated respiratory activity returned to control levels, at approximately 20 microM cytochrome c, establishing the threshold below which the turnover rate by cytochrome c oxidase in the cell depends on cytochrome concentration. Mildly damaged cardiac myocytes, as indicated by cell shortening, retention of visible striations and free-fluorescein exclusion, together with the absence of lactate dehydrogenase leakage and exclusion of trypan blue, were able to oxidize exogenous cytochrome c and were permeable to fluorescein-conjugated cytochrome c. The results, while consistent with an early cytochrome c release observed at the beginning of cell death, elucidate the role played by cytochrome c in the kinetic control of mitochondrial electron transfer under pathological conditions, particularly those involving the terminal part of the respiratory chain. These data are the first to demonstrate that the sarcolemma of cardiac myocytes, damaged but still viable, is permeable to cytochrome c.     

A cytochrome c from the hepatopancreas ofSepia officinalis L.

Riassunto Una emoproteina è stata estratta e parzialmente purificata dall'epatopancreas diSepia officinalis. Essa è ossidata dal ferricianuro e ridotta dall'acido ascorbico; gli spettri di assorbimento delle due forme, ossidata e ridotta, sono quelli tipici del citocromo c di mammifero.In comune con quest'ultimo il citocromo estratto dall'epatopancreas di sepia ha diverse altre proprietà come per esempio quella di non dare un emocromogeno con la piridina e di non perdere il gruppo prostetico dopo trattamento con acetone acido. A differenza del citocromo c di mammifero, il pigmento di sepia non resiste al calore e agli acidi; è precipitato dal solfato di ammonio al 75% di saturazione e sedimenta dopo prolungata centrifugazione a 105000×g. Non è ossidato dalla citocromossidasi di mammifero.

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This work has been supported by a grant (RG-4548) of the U.S. Public Health Service.     

Chromatographic forms of baker's yeast cytochrome c

Résumé Les auteurs ont étudié les caractéristiques de trois fractions obtenues par l'extraction du citochrome c de la levure. La première est la forme naturelle, tandis qu'on peut considérer les autres comme des formes artificielles résultant du procédé d'extraction.     

Effect of temperature on the activity of AMP-deaminase from rat heart

Summary In the presence of 1 mM ATP, the plots of Michaelis dependence of the reaction catalysed by AMP-deaminase from rat heart were hyperbolic at all temperatures between 10 and 40°C. Calculation of the energy of activation for ATP-activated enzyme and of the enzyme-substrate complex formation is presented.     

Effect of temperature on the activity of AMP-deaminase from rat heart.

In the presence of 1 mM ATP, the plots of Michaelis dependence of the reaction catalysed by AMP-deaminase from rat heart were hyperbolic at all temperatures between 10 and 40 degrees C. Calculation of the energy of activation for ATP-activated enzyme and of the enzyme-substrate complex formation is presented.     

Partial purification of a plasma-kinin-forming enzyme from horse urine

Zusammenfassung Durch Chromatographie mit Diäthylamino-äthyl-cellulose nach Ammoniumsulfat-Fraktionierung wurde ein Plasma-Kinin-freisetzendes Ferment aus Pferdeharn teilweise (80×) gereinigt. Das so gereinigte Präparat war gegen Pferde-, Menschen-, Rinder (Fraktion IV-4)- und Ratten-Blutplasma, nicht aber gegen Schweine-(Fraktion IV-4)-Globuline wirksam. Durch Sojabohnen-Trypsininhibitor oder Ovomucoid erfolgt keine Hemmung. Präparate von verschiedenem Reinheitsgrad zeigten entsprechendep-Toluenesulfonyl-l-arginin-methylester-spaltende und Kinin-freisetzende Wirksamkeit.

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Read before the XIIth Annual Meeting of the Sociedade Brasileira para o Progresso da Ciência, Piracicaba, July 1960; supported by Grant No. 58217 from the Rockefeller Foundation.     

The possible role of isoforms of cytochrome c oxidase subunit VIa in mammalian thermogenesis

A single cDNA of cytochrome c oxidase subunit VIa was characterised from liver, heart and the thermogenic organ of the partially endotherm tuna fish. The amino acid sequence revealed high identity with subunit VIa from carp and trout, but low identity to subunits VIaL (liver type) and VIaH (heart type) of mammalian cytochrome c oxidase. In reconstituted cytochrome c oxidase from bovine heart, the H ⁺/e⁻ stoichiometry is decreased from 1.0 to 0.5 at high intraliposomal ATP/ADP ratios via exchange of bound ADP by ATP at the matrix domain of the transmembraneous subunit VIaH. Reconstituted cytochrome c oxidase from bovine liver and kidney, containing subunit VIaL, revealed H ⁺/e⁻ ratios below 0.5, independent of the ATP/ADP ratio. The results suggest the evolution of three types of subunit VIa. Subunits VIaH and VIaL are postulated to participate in mammalian thermogenesis. Received 3 May 1999; received after revision 10 June 1999; accepted 29 June 1999     

The effect of ferrimyoglobin on the oxidation of succinic acid by horse heart muscle preparations

Riassunto L'autore ha studiato l'azione della metamioglobina sul sistema succinossidasico. È stata riscontrata una netta inibizione che sembra essere specifica per la succinodeidrogenasi. Tale inibizione non è influenzata dall'aggiunta di bleu di metilene ma invece completamente rimossa dal KCN in presenza di bleu di metilene. L'inibizione provocata dalla metamioglobina sulla succinossidasi aumenta nel tempo.

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Aided by a grant of the Rockefeller Foundation and the Consiglio Nazionale delle Ricerche.     

ATPase activity of guinea pig heart muscle

Riassunto L'Autore ha studiato l'influenza della concentrazione degli ioni Ca⁺⁺ e Mg⁺⁺ sull'ATPasi degli atri e dei ventricoli di cuore di cavia. Tale attività è maggiore a pH 9,2 che a pH 6,8. Mentre il Ca⁺⁺ influisce differenziando decisamente le attività degli atri da quelle dei ventricoli, il Mg⁺⁺ accentua piuttosto una differenza tra la parte destra e la sinistra. Il calore distrugge quasi completamente l'attività enzimatica dopo una permanenza a 60° per 20 min.