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PubMed1976

[Zincporphyrin pigments in the botryoid tissue of Haemopis sanguisuga L. and their localization by diaminobenzidine-H2O2 reaction (author's transl)].

From isolated botrydiosomes of Haemopis sanguisuga L. a pigment was extracted, separated by preparative paper chromatography and analysed chemically. Chromatographically the pigment was found to be composed of two fractions, which has been identified as zincporphyrin compounds, which are able to oxidize of diaminobenzidine in the presence of H2O2. As proved by ultrahistochemical method, the product of hte diaminobenzidine-H2O2 reaction is associated in the botryoid cells with the tubules foth of the endoplasmic reticulum and of botrydiosomes. The proboble functions of the zincporphyrins in the oxidizing processes are discussed.

3,3'-Diaminobenzidine↗
PubMed1976

Amino acid metabolism and protein synthesis in streptomycin resistant Vibrio El Tor.

Metabolic activities in relation to protein synthesis and amino acid utilization are altered in Vibrio El Tor after development of resistance towards streptomycin. Efficiency of in vivo and in vitro protein synthesis is markedly reduced in streptomycin resistant Vibrio El Tor. The rate of incorporation of 14C-amino acids into protein, uptake of 14C-valine and oxidation of certain amino acids are also altered.

Amino Acids↗
PubMed1976

Studies on platelet plasma membranes. I. Characterization of surface proteins of human platelets labeled with diazotized (125i)-diiodosulfanilic acid.

A polar, nonpenetrating compound of high specific activity, diazotized (125I)-diiodosulfanilic acid (DD125ISA), has been developed as a label for exposed proteins of the human platelet plasma membrane, and platelet proteins and the pattern of labeling have been studied with sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). That DD125ISA binds specifically to membrane proteins was demonstrated by: (1) the specific activity of isolated membrane protein was five to seven times that of whole platelet protein and (2) no proteins of intact platelets were labeled which were not represented in the isolated plasma membrane. That the DD125ISA-labeled membrane proteins were exposed on the cell surface was demonstrated by: (1) DD125ISA-labeled proteins were altered by trypsin treatment of intact, labeled platelets and (2) the pattern of labeling produced by reaction of isolated membranes with DD125ISA was quite different from that produced by the labeling of intact platelets. Analysis of platelet membrane proteins by SDS-PAGE demonstrated the glycoproteins previously described at 150,000 daltons (termed glycoprotein I) and 92,000 daltons (glycoprotein III) but we could discriminate two apparently distinct glycoproteins in the intermediate region (IIa: 125,000 daltons, and II: 118,000 daltons). Glycoproteins I and III were constant whereas IIa was clearly visible only in unreduced samples and II was predominant in reduced samples. Reaction of DD125ISA with intact platelets resulted in equal labeling of three of these four membrane glycoproteins (IIa, II, and III). The pattern of exposed proteins on the platelet surface labeled by DD125ISA was different from lactoperoxidase-131I, which labeled predominantly the 92,000 dalton glycoprotein, as demonstrated by simultaneous SDS-PAGE analysis. Therefore three glycoproteins of the human platelet plasma membrane are exposed to a radioisotope probe on the platelet surface and are accessible for contact interactions.

Azo Compounds↗
PubMedDate not supplied

Oxisuran reduction by rabbit tissue preparations.

Oxisuran, 2-((methylsulfinyl)acetyl)pyridine is reduced to alpha-((methylsulfinyl)methyl-2-pyridinemethanol, oxisuranol, by cytoplasmic enzymes from rabbit liver, kidney, brain, intestine, and lung. The cytoplasmic enzyme from liver is dependent on NADPH as cofactor and has an optimal pH of 6.0. Enzymatic activity is also present in liver mitochondria but at a lower specific activity. The cytoplasmic extracts catalyze the formation of two oxisuranol products, presumably the diastereoisomers described by Di Carlo and associates from in vivo studies. Verification of the product as oxisuranol was accomplished by thin-layer chromatography and mass spectrometry.

Animals↗
PubMed1976

Mechanism of the irreversible inhibition of aspartate aminotransferase by the bacterial toxin L-2-amino-4-methoxy-trans-3-butenoic acid.

The naturally occurring toxin L-2-amino-4-methoxy-trans-3-butenoic (AMB) acid irreversibly inhibits pyridoxal phosphate-linked aspartate aminotransferase. The inhibitor is a substrate for the enzyme, and as such is converted into a highly reactive intermediate which chemically reacts with an active site residue, thus irreversibly inactivating the enzyme. Enzymological and model studies on AMB are presented which enable one to determine the precise mechanism of action of this toxin. The mechanism involves Schiff base formation between the enzyme and toxin followed by alpha-C--H bond cleavage and aldimine isomerization to generate a bifunctional Michael acceptor. This molecule alkylates an active site residue by an addition and elimination route.

Aminobutyrates↗
PubMed1976

Differential reactivity of the two active site cysteine residues generated on reduction of pig heart lipoamide dehydrogenase.

Reduction of the active center disulfide bond in the flavoprotein pig heart lipoamide dehydrogenase generates two sulfur moieties which are chemically inequivalent in the 2-electron reduced form of the enzyme. Thus 1 cysteine residue is at least 13-fold more reactive than its partner toward iodoacetamide at pH 7.6. This selectivity was demonstrated by reaction of the 2-electron reduced enzyme with a low concentration of iodo[1-14C]acetamide under anaerobic conditions. The formation of a monolabeled derivative is accompanied by the reappearance of a spectrum of oxidized bound flavin, clearly different from that of the native enzyme. Alkylation of the remaining cysteine residues with iodo[12C]acetamide enabled the isolation of a tryptic version of the active center disulfide peptide. A single chymotryptic cleavage between the 2 alkylated cysteine residues generated a cationic and an anionic fragment containing 7% and 93% of the radioactivity of the purified tryptic peptide, respectively. The monolabeled derivative is catalytically inactive toward reduced or oxidized lipoamide, but is approximately 2-fold better as a transhydrogenase than the native protein using NADH and acetylpyridine adenine dinucleotide as substrates. Anaerobic titration with NADH leads to reduction of the flavin with concomitant formation of long wavelength absorption of low intensity. No intermediate reduced states were detected in this titration analogous to the red 2-electron form observed with the native enzyme. Similarly, intermediates during reduction of the enzyme by 1 eq of dithionite have not been detected.

Anaerobiosis↗
PubMed1976

Dissociation of CO from carboxyhemoglobin.

The reaction between carboxyhemoglobin and reduced microperoxidase (MP): Hb4(CO)4 + 4MP=Hb4 + 4MPCO, recently reported by us, has been further studied. By generating species Hb4(CO), Hb4(CO)2, and Hb(CO)3 in the stopped flow cuvette by the reaction of dithionite with the species of the general formula Hb4(O2)x(CO)y(x + y=4) in the presence of microperoxidase it has been possible to determine the stepwise CO dissociation rate constants l4, l3, l2, and l1. The overall CO dissociation rate constant l, which is the same in this system as l4, is not affected by 2,3-diphosphoglyceric acid. The activation energy of the reaction is 21,400 cal in 15-25 degrees range. The ratio deltal/deltapH is approximately 3 in 6.5 to 7.5 pH range. The kinetic data indicate that, compared to HbO2, the contribution to the cooperativity of the dissociation rate constants of carboxyhemoglobin is greatly reduced. The ligand-dependent differences in the reactions of Hb with CO, O2, and NO suggest that in the combination reactions the ligand plays an active role in the rate-limiting step.

Carbon Monoxide↗
PubMed1977

Antigenic studies of a VH fragment: demonstration of three sets of antigens, idiotypic, VH subgroup, and VH framework-specific antigens.

The antigenic properties of the VH region of immunoglobulin heavy chains were studied by means of a fragment corresponding to the variable part of the heavy chain of an IgG3 myeloma protein (KUP) and an antiserum made against this fragment. By hemagglutination, hemagglutination inhibition, and immunofluorescence techniques, it was shown that the anti-VH antiserum detected three sets of antigens in the VH region, namely idiotypic antigens, VH subgroup-specific antigens, and VH domain-(framework) specific antigens. The VH fragment inhibited in a VHII subgroup-specific hemagglutination inhibition test system. The VH fragment was thus antigenically similar to the tvh region found in the intact molecules and the light chains were not needed to express the VH subgroup antigens or the VH framework antigens.

Alkylation↗
PubMed1976

[Mechanisms and ways of regulation of lipoic acid penetration into biological structures].

Experimental evidence of the penetration of low doses (100--120 mkM) of lipoic acid (LA) into cells and mitochondria by means of transport systems, involving proteins was obtained. The functioning of those systems is regulated by hormones, is dependent of redox states, is disturbed in the presence of energy metabolism inhibitors and is stimulated by repeated injections of LA. The penetration of LA into erythrocytes is facilitated by a concentration gradient K+ and Na+ and the high activity of transport ATPases. In case of high (over 120 mkM) content of lipoate in the incubation medium, its penetration into the cells and mitochondria occurs largely due to ordinary diffusion. Such penetration of LA predominantly occurs also under conditions of transversely directed gravitational overloading (6g). The rate of LA penetration into the biological structures of the organism is regulated by complicated and efficient mechanisms, involving hormonal control of protein biosynthesis.

Adenosine Triphosphatases↗
PubMed1976

Collaborative study of a spectrofluorometric assay for Rauwolfia serpentina tablets and powdered root.

Reserpine-rescinnamine group alkaloids are extracted from Rauwolfia serpentina preparations into a dimethylsulfoxide (DMSO)-methanol mixture and diluted with 0.5N H2SO4. The chloroform extract of this solution is passed through a 0.1N NaOH-Celite column and then through a silica gel column. The weakly basic alkaloids trapped on the latter column are eluted with a methanol mixture; a portion of the eluate is treated with nitrous acid and the reserpine-rescinnamine content is determined by measuring the intensity of fluorescence of the oxidation product. The following means and standard deviations (11 collaborators) were obtained for the determination of reserpine-rescinnamine group alkaloids in 4 samples of Rauwolfia serpentina (NF reference powder, 100 mg and 50 mg commercial tablets, and a 45 mg synthetic tablet formulation) : 0.174% +/- 0.0112, 0.131% +/- 0.0047, 0.160% +/- 0.0100, and 0.153% +/- 0.0083, respectively.

Indicators and Reagents↗
PubMedDate not supplied

[The mechanism of action of d-amino acid oxidase. I. Evidence for a free radical mechanism of the reaction catalyzed b a dimeric form of the enzyme].

d-Amino acid oxidase can oxidize the substrate to a ketoacid in the absence of oxygen. The stoichiometry of this reaction is precisely 1 molecule of keto acid for 1 molecule of enzyme, containing two flavin groups. Hence, the flavin must be in the semi-reduced free radical state. But these free radicals cannot be visualized by ESR spectroscopy because of closeness and strong interaction. After the acid denaturation of the protein the coenzyme is released as a semi-reduced free radical. An alternative method of registration is the transfer of the free radical state to an added excess of free flavin molecules. By both methods it is quantitatively determined that each flavin of the enzyme is reduced to a free radical. Therefore, we believe to have evidenced unambiguously that this enzymatic reaction proceeds via a free radical transition state.

Animals↗
PubMed1976

Crystalline free radical of chloropromazine.

The method of preparation and the spectral characteristic of the crystalline free radical of chlorpromazine are described. Two absorption maxima at 770 and 860 nm concomitant with those at 530 and 277 nm were found. The highest rate of dismutation of the radical was 4-4.10(-1) M. sec-1 at pH 7-2. The mechanism of luminescence during the decay of the peroxide form of th radical is discussed.

Chemical Phenomena↗