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Biomedical subjects

S Pagani

Publications and source records attributed to S Pagani.

54 records · Page 3Linked to original sources
PubMed1989

Thymopentin administration and increase of sero-conversion after B-hepatitis vaccine in diabetic patients.

We have previously reported that 40% of diabetic patients have an impaired specific immune response after vaccination against B-hepatitis. Thymopentin (TP5), the active site of thymopoietin hormone, has been shown to increase antibody response (HbsAb) following B-hepatitis vaccination in several disease conditions. In the present study TP5 (50 mg) was administered subcutaneously three times per week to 17 diabetic patients for a week prior B-hepatitis vaccination and for three weeks afterwards. Sero-conversion was observed after the third dose of vaccine in 15 out of 17 (88%) patients and in 94% of a group of normal subjects acting as control. Although the median HbsAb titre was significantly lower in diabetics compared to normal subjects, we conclude that administration of TP5 in diabetic patients increases the rate of sero-conversion following B-hepatitis vaccination.

Adjuvants, Immunologic↗
PubMed1987

Nitrogenase of Klebsiella pneumoniae. Rhodanese-catalysed restoration of activity of the inactive 2Fe species of the Fe protein.

The inactive 2Fe species of the Fe protein of the nitrogenase of Klebsiella pneumoniae was generated by treating oxidized Fe protein (Kp2) with MgATP and chelator. Incubation of the 2Fe species of Kp2 with the sulphurtransferase rhodanese in the presence of thiosulphate, ferric citrate and reduced lipoate reproducibly restored activity. The extent of restoration of activity depended on the molar ratio of 2Fe Kp2 to rhodanese and was time-dependent. Re-activation did not occur in the reaction mixture lacking rhodanese.

Enzyme Activation↗
PubMed1987

In vivo determination of cell mediated immune response in diabetic patients using a multiple intradermal antigen dispenser.

The in vivo cell mediated immune response using a multiple intradermal antigen dispenser (Multitest) was evaluated in 99 diabetic patients (24 Type I and 75 Type II) and in 50 age matched normal subjects. Seven different antigens (tetanus, diphteria, streptococcus, tubercoline, candida, trichophyton, proteus and a glycerine control) were applied in the forearm and the induration for the antigens tested was measured 48 hours later. A score was calculated adding the arithmetic means obtained with each single antigen. Overall we did not find major differences between diabetic patients and controls except Type I patients of shorter duration (less than 5 years) having a reduced response (p less than 0.05) and both Type I and Type II patients showing an elevated response to candida antigen (p less than 0.001). No correlation was found between the intradermal response and metabolic control. As the intradermal test is a model for delayed type of hypersensitivity, these data suggest that the in vivo lymphocyte to lymphocyte cooperation in patients with long standing diabetes is not impaired.

Adult↗
PubMed1986

Removal of ferritin-bound iron by DL-dihydrolipoate and DL-dihydrolipoamide.

The naturally occurring dithiols DL-dihydrolipoate and DL-dihydrolipoamide were tested for their ability in the removal of ferritin-bound iron. Both compounds remove the iron stored inside the protein by complexing it in the ferric form. The iron can be reduced to the ferrous form by excess dithiol, but this is not necessary for complete removal. Reaction is complete in few hours and, at molar ratios of chelator to metal higher than 10, more than 60% of the ferritin-bound iron was removed. The amount of iron stored in the ferritin molecule does not affect the rate and the yield of the removal reaction. The iron-removing ability of DL-dihydrolipoate was found to be identical to that of an equimolar solution of sodium dithionite, and to be pH-dependent. Results are discussed in terms of the molecular architecture of ferritin and of the chelators, and their possible physiological relevance is pointed out.

Chromatography, Gel↗
PubMed1985

Enzymic synthesis of the 4Fe-4S clusters of Clostridium pasteurianum ferredoxin.

Ex novo enzymic synthesis of the two 4Fe-4S clusters of Clostridium pasteurianum ferredoxin has been achieved by incubation of the apoprotein with catalytic amounts of the sulfurtransferase rhodanese in the presence of thiosulfate, DL-dihydrolipoate and ferric ammonium citrate. This enzymic reconstitution procedure was compared to a chemical one, in which the enzyme was replaced by sodium sulfide. A further comparison was made with the results previously obtained in the enzymic synthesis of the 2Fe-2S cluster of spinach ferredoxin, allowing the following conclusions to be drawn. The nature of the cluster to be inserted into the reconstituted iron-sulfur protein is determined by the apoprotein itself. The refolding of the structure of the iron-sulfur proteins around the newly inserted cluster is the rate-limiting step in both chemical and enzymic reconstitution. Rhodanese appears to play a role in the recovery of the native architecture of the reconstituted iron-sulfur protein(s). The extension to the 4Fe-4S centers of the rhodanese-based biosynthetic system allows this enzymic route to be proposed as a general way to the in vivo synthesis of iron-sulfur structures.

Apoproteins↗
PubMed1984

Enzymic synthesis of the iron-sulfur cluster of spinach ferredoxin.

A biologically active spinach ferredoxin was reconstituted from the apoprotein by incubation with catalytic amounts of the sulfurtransferase rhodanese in the presence of thiosulfate, reduced lipoate and ferric ammonium citrate. Analytical and spectroscopical features of the reconstituted ferredoxin were identical to those of the native one; yield of the reconstitution reaction was 80%. Yields and kinetic parameters of the enzymic and chemical reconstitution were also compared. The higher efficiency of the enzymic system is ascribed to a productive interaction between rhodanese and apoferredoxin favouring the process of cluster build-up and insertion. The physiological relevance of this synthetic activity is discussed.

Animals↗
PubMed1983

Modification of the thermodynamic properties of the electron-transferring groups in mitochondrial succinate dehydrogenase upon binding of succinate.

The redox properties of the covalently-bound flavin and of the tetrahedral iron-sulfur center S1 of succinate dehydrogenase were studied as a function of the binding of different ligands to the enzyme. The midpoint potential of both flavin and S1 increases by some 200 mV when protein binds succinate to a site having Kdsucc = 0.8-1.0 mM, thus different from the substrate binding site. Succinate binding increases the potential of the oxidized flavin/semiquinone half-cell more than that of the semiquinone/reduced flavin one: this results in higher semiquinone formation with increasing succinate. Malonate and fumarate appear to mimic, in this regard, the effect of succinate. The increase in midpoint potential of S1 upon binding of dicarboxylic acid is related to an increase in hydrophobicity of the cluster environment. The possible molecular basis for the modulation of the flavin potential is discussed together with the significance of this shift on the catalytic behaviour of the protein.

Binding Sites↗
PubMed1983

Interaction of rhodanese with mitochondrial NADH dehydrogenase.

NADH dehydrogenase is an iron-sulfur flavoprotein which is isolated and purified from Complex I (mitochondrial NADH: ubiquinone oxidoreductase) by resolution with NaClO4. The activity of the enzyme (followed as NADH: 2-methylnaphthoquinone oxidoreductase) increases linearly with protein concentration (in the range between 0.2 and 1.0 mg/ml) and decreases with aging upon incubation on ice. In the present work a good correlation was found between enzymic activity and labile sulfide content, at least within the limits of sensitivity of the assays employed. Rhodanese (thiosulfate: cyanide sulfurtransferase (EC 2.8.1.1) purified from bovine liver mitochondria was shown to restore, in the presence of thiosulfate, the activity of the partly inactivated NADH dehydrogenase. Concomitantly, sulfur was transferred from thiosulfate to the flavoprotein and incorporated as acid-labile sulfide. Rhodanese-mediated sulfide transfer was directly demonstrated when the reactivation of NADH dehydrogenase was performed in the presence of radioactive thiosulfate (labeled in the outer sulfur) and the 35S-loaded flavoprotein was re-isolated by gel filtration chromatography. The results indicated that the [35S]sulfide was inserted in NADH dehydrogenase and appeared to constitute the structural basis for the increase in enzymic activity.

Animals↗
PubMed1983

The inhibition of rhodanese by lipoate and iron-sulfur proteins.

A study was made on the effects of DL-dihydrolipoate, lipoate and iron-sulfur proteins on the activity of rhodanese (EC 2.8.1.1) with dihydrolipoate or cyanide as acceptors. DL-Dihydrolipoate inactivates rhodanese, lipoate does not, and the opposite occurs with the sulfur-free form of the transferase. The observed effects vary with the sulfane sulfur acceptor from rhodanese (i.e., dihydrolipoate or cyanide) and depend on intramolecular oxidation of the catalytic sulfhydryl or on formation of a mixed disulfide with dihydrolipoate. Thiosulfate protects against inactivation by reloading the active-site cysteine with persulfide sulfur. The inhibition of sulfur transfer by iron-sulfur proteins appears related to the amount of native iron-sulfur structure interacting with rhodanese. The implications of the results for a possible biological role of rhodanese are considered.

Animals↗
PubMed1981

Catalytic and molecular modifications of succinate dehydrogenase by monovalent inorganic anions.

The enzymatic activity and the oxidation state of soluble, activated, substrate-reduced succinate dehydrogenase are modified by the presence of bromide. The anion inhibits the enzyme by two different mechanisms which depend on the ratio of bromide to succinate. At high ratios binding of two bromide ions is required and a competitive inhibition is observed: removal of succinate from the substrate binding site (Kd = 0.1 mM) leads to oxidation of the flavin. At lower ratios but with sufficient succinate to saturate a site with Kd = 1.52 mM, uncompetitive inhibition by a single bromide ion is observed. Mechanisms, as well as the possible physiological significance of the novel type of regulation of succinate dehydrogenase, are discussed.

Anions↗
PubMed1980

Modulation of the flavin redox potential as mode of regulation of succinate dehydrogenase activity.

The redox properties of flavin in active and non-active (oxaloacetate reacted) soluble succinate dehydrogenase were studied. Quantitative analysis of reductive activation titrations of redox titrations of active and non-active enzyme reveal that the redox potential of the histidyl-flavin in the active enzyme (-3 +/- 15 mV) is high enough to allow reduction by succinate, whereas in the non active enzyme it is -196 +/- 19 mV, far to low to be reduced by substrate. The flavin radical in the active enzyme attains 60% of total flavin at a poised redox potential of about +60 mV, upon addition of oxaloacetate the magnitude of the signal is diminished and the potential where it reaches maximal concentration is shifted by about -200 mV. A mechanism is proposed which ascribes the fundamental difference between active and non-active enzyme to the inability of the latter to be reduced by substrate.

Animals↗
PubMed1977

Rhodanese-Mediated sulfur transfer to succinate dehydrogenase.

The interaction of the sulfurtransferase rhodanese (EC 2.8.1.1) with succinate dehydrogenase (EC 1.3.99.1), yeast alcohol dehydrogenase (EC 1.1.1.1) and bovine serum albumin was studied. Succinate dehydrogenase incorporates the sulfane sulfur of [35S]rhodanese and, in the presence of unlabelled rhodanese, also incorporates that of [35S]thiosulfate. Rhodanese releases most of its transferable sulfur and is re-loaded in the presence of thiosulfate. Rhodanese undergoes similar modifications with yeast alcohol dehydrogenase but this latter does not bind 35S in amounts comparable to those incorporated in succinate dehydrogenase: nearly all the 35S released by [35S]rhodanese is with low-molecular-weight compounds. Bovine serum albumin also binds very little sulfur and [35S]rhodanese present in the reaction mixture does not discharge its radioactive sulfur nor does it take up sulfur from thiosulfate. Sulfur release from rhodanese appears to depend on the presence of - SH groups in the acceptor protein. Sulfur incorporated into succinate dehydrogenase was analytically determined as sulfide. A comparison of the optical spectra of succinate dehydrogenase preparations incubated with or without rhodanese indicates that there is an effect of the sulfurtransferase on the iron-sulfur absorption of the flavorprotein. The interaction of rhodanese with succinate dehydrogenase greatly decreases the catalytic activity of rhodanese with respect to thiocyanate formation. This is attributed to modifications in rhodanese associated with the reduction of sulfane sulfur to sulfide. Thiosulfate in part protects from this deactivation. The reconstitutive capacity of succinate dehydrogenase increased in parallel with sulfur incorporated in that enzyme following its interaction with rhodanese.

Alcohol Oxidoreductases↗