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PubMed1978

The reversible binding of oxygen to sulfhemoglobin.

The O2 binding properties of sulfhemoglobin were studied. The oxygen tension required for half-saturation of sulfhemoglobin is more than 2 orders of magnitude higher than that for hemoglobin A. The binding of O2 exhibits an alkaline Bohr effect larger than that observed for hemoglobin, yet the Hill number is unity. From the Bohr titration curve, 0.68 proton is released during O2 binding at 0 degrees C. Sulfhemoglobin prepared from carboxypeptidase A-treated hemoglobin has an affinity for O2 which is about the same as that of sulfhemoglobin at the theoretical limit of the Bohr titration curve. Like its carboxypeptidase A-treated hemoglobin precursor, this sulfhemoglobin does not bind O2 cooperatively. Thus, sulfhemoglobin appears to be in a high affinity form at alkaline pH and a low affinity form at acid pH, similar to hemoglobin A. These results demonstrate that the magnitude of the Hill number is not always an indicator of the interaction between oxygen binding and other functions in a hemoglobin.

Carboxypeptidases↗

PubMed1992

1H nuclear magnetic resonance study of the prosthetic group in sulfhemoglobin.

The molecular and electronic structure of the modified prosthetic group of sulfhemoglobin (SHb) was investigated by 1H NMR for the low-spin ferric cyano-met and high-spin ferrous deoxy sulfhemoglobin complex. The 1H NMR resonances of the two subunits in the cyano-met SHb complex were differentiated on the basis of the differential stability toward regeneration of native subunits. The subunit origin for the two sets of resonances was established by formation of the sulfglobin protein for the isolated alpha-chain prior to assembling with the native beta-subunit to yield a tetramer with sulfhemin in the alpha-subunits. The subunit peak assignments establish that it is the beta-subunit of SHb which regenerates more rapidly to native protein. The hyperfine shifted sulfhemin peaks were assigned based on steady-state nuclear Overhauser effects which demonstrated that similarly hyperfine shifted peaks exhibit the same dipolar connectivities observed in the analogous sulfmyoglobin complex. Hence it is concluded that pyrrole B is the site of reaction in both hemoglobin and myoglobin. The initially formed SHb complex failed to equilibrate to yield a complex with a sulfhemin sufficiently stable to extraction as found previously for sulfmyoglobin. However, apoHb readily bound the green sulfhemin extracted from the terminal alkaline equilibration product of sulfmyoglobin. The inhibition on the equilibration to the alkaline form with the exocyclic thiolene ring is attributed to the interaction with Val FG5. The observations of the same dipolar connectivities among similarly hyperfine shifted peaks in the directly prepared and reconstituted SHb complexes further support the same structure for the sulfhemin in sulfmyoglobin and SHb. The strongly hyperfine shifted peaks in the deoxy form of both SHb complexes were found very similar to those of the analogous sulfmyoglobin complexes. The proximal His labile ring proton signal appears to experience a 5- to 10-ppm decrease upon conversion of a native globin to sulfglobin. This attenuation may provide a probe for differentiating chlorins and hemins in globin pockets.

Humans↗

PubMedDate not supplied

Sulfhemoglobinated erythrocytes as an optical intravascular tracer in the lung.

Sulfhemoglobinated erythrocytes (SHb-RBC's) were examined for utility as an optical multiple indicator dilution tracer in lung studies. A device was developed to measure this tracer optically in flowing blood. Arterial blood was sampled from cannulated, anesthetized dogs and pumped through the device that measured the optical density (OD) of blood at 620 nm. This system was calibrated for increasing SHb-RBC concentrations using an unsteady-state indicator dilution procedure. Areas under optical density (delta OD) profiles were well correlated with injected SHb-RBC volumes using linear regression (r2 > 0.9). This linearity was independent of blood oxygenation, hematocrit, or pH. In vivo lung indicator dilution studies in the intact dog were performed and compared to radioisotope indicator studies using 51Cr labeled erythrocytes. Coefficient of variation (CV) between the two curves was 0.065 under baseline conditions, 0.085 for studies performed during hypoxia, and 0.073 after pH was lowered. We conclude that this device linearly measured SHb-RBC content in whole blood and that SHb-RBC is as accurate a lung indicator dilution tracer as 51Cr-erythrocytes.

Animals↗

PubMed1999

Sulfhemoglobin formation in human erythrocytes by cystalysin, an L-cysteine desulfhydrase from Treponema denticola.

Cystalysin, isolated from the oral pathogen Treponema denticola, is an L-cysteine desulfhydrase (producing pyruvate, ammonia and hydrogen sulfide from cysteine) that can modify hemoglobin and has hemolytic activity. Here, we show that enzymatic activity of recombinant cystalysin depends upon stochiometric pyridoxal phosphate. The enzyme was not functional as an L-alanine transaminase, and had a strong preference for L-cysteine over D-cysteine. Cystalysin preferred small alpha-L-amino acids as substrates or inhibitors and was far more active towards L-cysteine than towards the other standard amino acids that undergo pyridoxal phosphate-dependent beta-elimination reactions (serine, threonine, tryptophan and tyrosine). Cystalysin tolerated small modifications to the carboxylate of L-cysteine (i.e., the methyl and ethyl esters of L-cysteine were good substrates), but the smallest possible peptide with an N-terminal cysteine, L-cysteinylglycine, was a very poor substrate. These results, combined with the implicit requirement for a free amine for pyridoxal phosphate-dependent reactions, imply that cystalysin cannot catabolize cysteine residues located within peptides. Cystalysin has Michaelis-Menten kinetics towards L-cysteine, and there was little or no inhibition by ammonia, H2S, pyruvate and acetate. Human erythrocytes incubated with H2S or with cystalysin and cysteine primarily accumulated sulfhemoglobin and methemoglobin, along with minor amounts of choleglobin and protein aggregates. Erythrocytes retained the ability to reduce methemoglobin in the presence of H2S. Cystalysin could not modify hemoglobin when beta-chloroalanine was the substrate, indicating an absolute requirement for H2S production. Cystalysin appears to be an unregulated L-cysteine catabolizing enzyme, with the resulting H2S production being essential to the atypical hemolytic activity.

Cystathionine gamma-Lyase↗

PubMed1980

Microvessel mean transit time and blood flow velocity of sulfhemoglobin-RBC.

An indicator dilution technique is described for obtaining time-concentration curves subsequent to bolus injections of sulfhemoglobin red blood cells (SH-RBC), which have a deep greenish-brown color (absorption peak 620 nm vs. 542 and 564 nm for normal red cells). The series- and parallel-coupled microvessels of cat mesentery were studied. This is accomplished by means of video microscopy with a two-window intensity-sensitive video sampler system. The relationship between SH-RBC concentration in blood and optical measurement is linear. Blood flow velocities were calculated from the difference in mean transit times between two points along a vessel. When this technique is used in association with the previously reported method for determining time-concentration curves for the plasma indicator FITC-dextran the mean transit time (t) for red blood cells was less than for plasma in arterioles. The reproducibility of t and flow velocity for both SH-RBC and FITC-dextran from successive injections were reported. The mean transit time ratio of arteriolar SH-RBC to FITC-dextran averages 0.89. Blood flow velocity calculated from SH-RBC is greater than that calculated from FITC-dextran in these same arterioles. The ratio of the velocities averages 1.29.

Animals↗

PubMed1977

[Studies on sulfhemoglobin formation by various drugs (2) (author's transl)].

Sulfhemoglobin (SHb) and methemoglobin (MHb) formations by various aniline erivatives were examined by a single and three consecutive intraperitoneal administrations to mice. It was found that with a single administraion, methemoglobinemia was induced by aniline, 2-methylaniline, 3-methylaniline, 4-methylaniline, 3-trifluoromethylaniline (3-TFMA), 4-trifluoromethylaniline (4-TFMA), 2, 3-dichloroaniline, 2-aminopehnol, acetanilide (AA), 2-hydroxyacetanilide, N-methylaniline (NMA), N,N-dimethylaniline (NDMA), N-ethylaniline (NEA) and N,N-diethylaniline, and was not observed with 2, 3-dimethylanilnie, 2-trifluoromethylaniline, 3-aminophenol, 4-aminophenol, 2. 6-dichloroaniline, 3-hydroxyacetanilide (3-HAA), 4-hydroxyacetanilide (4-HAA), 2-aminobenzoic acid, 3-aminobenzoic acid, 4-aminobenzoic acid and 4-chloro-2-aminobenzoic acid. On the other hand, sulfhemoglobinemia which appeared much more delayed than MHb, with a single administration, was found to be induced by 3-TFMA, 4-TFMA and NMA. Furthermore, with three consecutive administrations, such was induced by AA, 3-HAA, NDMA and NEA even though SHb was not demonstrated with a single administration. Structure-SHb and MHb forming property relationships were discussed.

Aniline Compounds↗

PubMed1977

[Studies of sulfhemoglobin formation by various drugs (3) (author's transl)].

Sulfhemoglobin (SHb) and methemoglobin (MHb) formations by various compounds were examined by single and three consecutive intraperitoneal administrations to mice. With a single administration, methemoglobinemia was induced by diphenylamine (DPA), 1-naphthylamine (NA), phenylnaphthylamine (PNA), N-(1-naphthyl) anthranilic acid (N1) and N-(1'-naphthyl)-2-aminophenylacetic acid (IG240), and was not observed with phenylanthranilic acid (PAA), N-benzoyl-N'-phenyl-2, 6-diaminobenzoic acid (BPAA), flufenamic acid (FA), mefenamic acid (MFA), N-(2-6-dichlorophenyl) anthranilic acid (CPAA), N-(2', 6'-dichlorophenyl)-2-aminophenylacetic acid (CPPA), nine derivatives of N1 and two derivatives of IG240. On the other hand, sulfhemoglobinemia, with a single administration, was found to be induced by NA. Furthermore, with three consecutive administrations, such was induced by DPA, PAA, BPAA and FA even though SHb was not demonstrated with a single administration, and was not observed with MF, CPAA, CPPA and various derivatives of N1 and IG240.

1-Naphthylamine↗

PubMed1975

[Formation of sulfhemoglobin using various drugs].

It is well known that aniline and hydroxylamine derivatives induce methemoglobinemia in humans as well as various animal species. It was noticed that sulfhemoglobinemia was induced by subchronic administration of N-(4-chlorophenyl)-beta-(4-hydroxymethylphenoxy)ethylurethane (HPU) to rabbits (p.o.), cats (i.p.) and mice (i.p.). Sulfhemoglobin (SHb) and methemoglobin (MHb) formation by various compounds structurally related to HPU were examined by a single and three consecutive intraperitoneal administrations to mice. It was found that by a single administration, methemoglobinemia was induced by phenylhydroxylamine (PHA), nitrobenzene (NB), aniline (A), 2-chloro-A (2-Cl-A), 3-Cl-A, 4-Cl-A, acetanilide (AA), phenacetin (PA), N-(4-chlorophenyl)ethylurethane (CPU), hydroxylamine (HA) and sodium nitrite (SN), and was not observed with phenylurethane, HPU, methylhydroxylamine (MHA), methylamine and nitromethane (NM). On the other hand, with sulfhamoglobinemia which appeared much more delayed than MHb, a single administration, was found to be induced by PHA, 3-Cl-A, 4-Cl-A, PA, CPU, MHA and SN. Furthermore, with three consecutive administrations, such was induced by NB, 2-Cl-A, AA, HPU and NM even though SHb was not demonstrated with a single administration. Structure-SHb forming property relationship and mechanism for SHb formation are discussed.

Acetanilides↗

PubMed1986

Sulfhemoglobin. Properties of partially sulfurated tetramers.

The properties of sulfhemoglobin (sulfHb) were investigated using disc gel isoelectric focusing and optical spectrophotometry. Laboratory-prepared samples, which contained a high yield of sulfHb (70-85%), and a patient-derived sample, which contained a low yield (12%), contain a tetrameric population that reflects a random distribution of modified (sulfurated) subunits. Hybrid tetramers, i.e. those containing sulfurated and unmodified subunits, were resolved from fully sulfurated and unmodified hemoglobin upon electrofocusing of ferric or ferrous sulHb samples. The electrophoretic differences between ferric sulfHb and metHb arise from a difference in the pK for the met to hydroxymet conversion of sulfurated subunits (Carrico, R., Peisach, J., and Alben, J. O. (1978) J. Biol. Chem. 253, 2386-2391). Both partially and fully sulfurated tetramers, when in the deoxy form and when in the fully ligated CO form, co-focus with their unmodified deoxy-Hb and Hb CO counterparts. Thus, these sulfurated tetramers exhibit normal ligand-dependent ionization of Bohr protons. In air-equilibrated samples, hybrid tetramers are partially ligated as a result of the reduced O2 affinity of the sulfurated subunits. These partially ligated tetramers exhibit a pI intermediate between oxy-Hb and deoxy-Hb due to the fractional ionization of Bohr protons. The partially sulfurated, partially ligated tetramers as well as deoxy-sulfHb tetramers were found to bind 2,3-diphosphoglycerate in disc gels. Despite the preservation of these heterotropic effects, which are confirmed in CO binding studies in solution, fully sulfurated tetramers recovered using preparative isoelectric focusing exhibit little or no cooperativity.

Carbon Monoxide↗

PubMed1983

Oxido-reductive reactions of sulfhemoglobin with various reagents associated with changes in conformation of the protein.

The optical peaks at Soret region and near at 620 nm of sulfhemoglobin (sulfHb) shifted from 419.5 nm to 423 nm and from 623 nm to 619 nm, respectively, according to the decrease in oxygen concentrations of the sulfHb solution (1 atm to zero atm). This shift of optical peaks was strengthened by the addition of inositol hexaphosphate (P6-inositol), a strong allosteric effector of Hb. Thus the shift of the optical peaks seems to reflects the changes in conformation of sulfHb. In order to clarify the relationship between the conformation of sulfHb and the reactivity of the protein with various reagents, we studied the oxidation and reduction reaction of the protein with ascorbic acid, ferricyanide and nitrite under aerobic and anaerobic conditions. The results suggested that the rate of oxido-reductive reactions of ferrous and ferric sulf Hbs with these compounds are associated with the conformation of the protein.

Ascorbic Acid↗

PubMed1997

A case of sulfhemoglobinemia and emergency measurement of sulfhemoglobin with an OSM3 CO-oximeter.

We describe a case of sulfhemoglobinemia associated with toxic paint ingestion. Blood gases, oxygen content, and fractional hemoglobin derivatives were assayed with Radiometer 520 and OSM3 instruments. Although the CO-oximeters indicated the presence of sulfhemoglobin (SulfHb), the results were not quantitative. An OSM3 service software program was activated to obtain the actual concentrations of the hemoglobin fractions. Subsequently, we evaluated the performance of the OSM3 service program for the analysis of SulfHb by performing precision studies and comparing OSM3 results with those of an AVL 912 CO-oximeter. Retrospectively, we determined that the patient's specimens contained 6% SulfHb. There was an obvious deviation between standard OSM3 oxyhemoglobin fraction measurements and those obtained by using its service program-the effect of a high SulfHb content.

Adult↗

PubMed1968