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K Mawatari

Publications and source records attributed to K Mawatari.

65 records · Page 4Linked to original sources
PubMed1984

Quantitative evaluation for the role of beta 146 His and beta 143 His residues in the Bohr effect of human hemoglobin in the presence of 0.1 M chloride ion.

Two different methods were used to determine the number of Bohr protons released upon oxygenation of human hemoglobin (Hb A) and Hb A lacking beta 146 His (des-His Hb A) at the pH ranging from pH 5.0 to 9.0 in the presence of 0.1 M Cl- at 25 degrees C. One is the direct differential titration method, the other is based on the measurement of oxygen affinity as a function of pH. The results obtained for Hb A or des-His Hb A with two methods were completely mutually consistent. The number of Bohr protons released from des-His Hb A upon oxygenation at pH 7.5 was about 44% less than that from Hb A, while at pH 5.5 the number of Bohr protons taken up by des-His Hb A was 20% greater than that by Hb A. The differences in the number of Bohr protons between Hb A and des-His Hb A could not be simply ascribed to the lack of beta 146 His from Hb A. The pK alpha values, which were determined by the deuterium exchange method using 1H NMR, were 8.0 for beta 146 His of deoxy-Hb A and 6.5 for that of CO Hb A, while those of beta 143 His were 5.2 for deoxy-Hb A and 6.0 for CO Hb A. From these pK alpha values, in addition to those of alpha 1 Val proposed for the modified CO and deoxy-Hb A with carbamylated beta chains by Van Beek and De Bruin (Van Beek, G. M., and De Bruin, S. H. (1980) Eur. J. Biochem. 105, 353-360), it became evident that almost all (about 92%) of the alkaline Bohr protons released upon oxygenation of Hb A in the presence of 0.1 M Cl- could be accounted for by the protons from these 2 residues, although the involvement of other histidine residues could not be denied. About half the acid Bohr protons from Hb A, which corresponds to the higher pH part (above pH 5.0) of the acid Bohr effect, could be explained by the involvement of beta 143 His residue. The residual acid Bohr effect in the more acidic pH region was presumably contributed by an amino acid residue with pK alpha values of 4.05 and 5.95 for the deoxy- and CO Hb A, respectively, although the amino acid residue was unspecified.(ABSTRACT TRUNCATED AT 400 WORDS)

Chlorides↗
PubMed1983

Spectral changes upon subunit association in valency hybrid hemoglobins.

The absorption, circular dichroism (CD) and magnetic circular dichroism (MCD) spectra of valency hybrid hemoglobins and their constituents (alpha + and beta chains for alpha 2+beta 2, alpha and beta + chains for alpha 2 beta 2+: + denotes ferric heme) were measured in the Soret region for F-, H2O, N3- and CN- derivatives. Absorption and MCD spectra of valency hybrid hemoglobins were very similar to the arithmetic mean of respective spectra of their corresponding component chains in all derivatives. The Soret MCD intensity around 408 nm for various complexes of valency hybrid hemoglobins seems to reflect the spin state of ferric chains. Upon ferric and deoxy ferrous subunit association to make the deoxy valency hybrid hemoglobins, only the high-spin forms bound with F- and H2O of alpha 2+beta 2 displayed a blue shift in the peak position around 430 nm and those of alpha 2 beta 2+ an increase in intensity around 430 nm. The blue shift and the increase in intensity were considered to be caused by the structural changes in deoxy beta chains of alpha 2+beta 2 and deoxy alpha chains of alpha beta 2+, respectively. These spectral changes were interpreted on the basis of their oxygen-equilibrium properties. In contrast to absorption and MCD spectra, the CD spectra of valency hybrid hemoglobins were markedly different from the simple addition of those of their component chains in all derivatives examined. The large part of CD spectral changes upon subunit association were interpreted as changes in the heme vicinity accompanied by formation of the alpha 1 beta 1 subunit contact.

Absorption↗
PubMed1983

Magnetic circular dichroism and spin equilibrium of methemoglobin and its subunits.

The intensity of the Soret magnetic circular dichroism (MCD) spectra of various complexes of methemoglobin subunits (alpha + and beta +) as well as methemoglobin (metHb A) was correlated well with the spin states of ferric heme. Upon the subunit association, spin state transition toward higher spin was observed only in high spin derivatives and the changes in spin state were due to mainly those of beta + chains. The effect of an allostric effector, inositol hexaphosphate (IHP), on the MCD spectra of metHb A derivatives was observed much significantly for high spin forms than low spin ones.

Adult↗
PubMed1983

Different effects of subunit association upon absorption and circular dichroism spectra of methemoglobin.

Absorption and circular dichroism (CD) spectra of the Soret band, assigned as a pi-pi transition of the porphyrin pi-electron system, showed a great difference between alpha and beta subunits in the ferric state (alpha +, beta +). The nonequivalence of the spectra between alpha + and beta + subunits partly originates from the difference in the strength of the bond between heme iron and the proximal histidine. The peak positions for absorption and CD spectra of the ferric derivatives associated with F-, H2O, N-3 and CN- of the isolated subunits qualitatively correlate with the spin state of the ferric heme. The Soret absorption spectra obtained by simple addition of those for alpha + and beta + subunits are very similar to those for methemoglobin A (metHb A). On the other hand, the arithmetic means for the Soret CD spectra of alpha + and beta + subunits are different from those for metHb A. These differences were not observed between the Soret CD spectra of alpha 1 beta 1 dimer, which is predominantly present in metHb Hirose (beta 37Trp-Ser), and those of tetrameric metHb A. Therefore, the interaction between alpha 1 and beta 1 subunits to make the alpha 1 beta 1 dimer may strongly affect the CD spectral properties of alpha + and beta + subunits. The effect of the interaction between two homogeneous dimers, alpha 1 beta 1 and alpha 2 beta 2, forming a tetramer, on the Soret CD spectral properties, if any, is very small compared with that between alpha 1 and beta 1 subunits.

Circular Dichroism↗
PubMed1983

The contrasting effect of dietary phosphatidylethanolamine and phosphatidylcholine on serum lipoproteins and liver lipids in rats.

The effect of dietary phosphatidylethanolamine (PE) and phosphatidylcholine (PC) added to cholesterol-free semipurified diet on serum lipoprotein and hepatic and fecal lipids was compared to the effect on rats fed soybean oil (controls). The dietary PE, but not PC, caused a decrease in serum cholesterol, phospholipid, apolipoprotein A-I (apoA-I) and apoE and an increase in high molecular weight apoB. The simultaneous addition of PC and ethanolamine also decreased serum apoA-I and cholesterol. The distribution patterns of phospholipid subclasses in the liver and fatty acid composition of hepatic and plasma phospholipids were also altered by dietary PE. Both PE and PC increased to a similar extent the excretion of fecal neutral steroids and hepatic 3-hydroxy-3-methylglutaryl-coenzyme A reductase activity compared to the controls. The present study, therefore, demonstrated for the first time that the PE in the soybean phospholipid preparation is responsible for the alterations of profiles of serum lipids and apoproteins in rats.

Animals↗
PubMed1982

Tryptophan fluorescence of human hemoglobin. II. Effect of inositol hexaphosphate on the T-R transition.

Fluorescence spectra of tryptophan residues of human hemoglobin in the absence and presence of inositol hexaphosphate were measured at room temperature. The tryptophan fluorescence intensity of deoxy HbA was observed to decrease in accordance with the binding with inositol hexaphosphate. The fluorescence intensity of HbA, Hb Kempsey (beta 99 Asp-Asn), Hb Chesapeake (alpha 92 Arg-Leu) and NES-des-Arg Hb (des-141 alpha Arg and beta 93 Cys-N-ethylsuccinimide derivative) in the presence of inositol hexaphosphate exhibits a considerable decrease in the deoxy to oxy transition, while no or slight fluorescence intensity change was observed in the deoxy to oxy transition of Hb Kempsey and NES-des-Arg Hb in the absence of inositol hexaphosphate. The tryptophan fluorescence behavior suggest that the inositol hexaphosphate-induced structural change in these hemoglobins is attributable to the formation of a different T type of structure from that of the normal T-R transition.

Hemoglobin A↗
PubMed1981

Two-state analysis for allosteric properties of abnormal hemoglobins.

To shed light upon the understanding of structure and function relationship of hemoglobin, we determined the oxygen equilibrium curves of a series of alpha 1 beta 2 contact anomalous hemoglobins, low and high spin derivatives of valency hybrid hemoglobins and normal hemoglobin under various conditions comparable with each other using an automatic recording apparatus. The Hill plots of their curves were analyzed by a trial and error method without any assumptions using computer graphic display. The results deduced from these analyses are as follows. Anomaly in alpha 1 beta 2 contact region, weakening or rupture of the Bohr effect and Cl- dependent salt-bridges, small displacement of heme iron from porphyrin plane result in not only shifting the R--T equilibrium towards R but also raising the oxygen affinity of the T state to various extents. IHP binding can oppose these effects. A relation that the change in L strongly depends upon the change in c was newly discovered. These results suggest that the T state of individual Hb takes a single structure of many heterogeneous T quaternary structures depending on its function.

Allosteric Regulation↗
PubMedDate not supplied

The potential risk for upper extremity thromboembolism in patients with occluded axillofemoral bypass grafts: two case reports.

Axillofemoral bypass grafts (AxFG) are widely used in the management of poor-risk patients with aortoiliac occlusive disease. On the other hand, AxFGs are associated with a variety complications to the upper extremity (UE). UE thromboembolism represents a significant and specific complication of occluded AxFGs in our series (2.6% of patients, 33.3% of occluded grafts). This article describes two cases of late axillary artery thrombosis caused by the occlusion of externally-supported AxFGs. The two patients were treated by graft disconnection, a distal embolectomy, and patch angioplasty of the axillary artery. Their postoperative courses were uneventful. Based on the authors' experience and a review of the literature, they suggest that an occluded AxFG represents a high risk for use of a donor artery and that such patients must therefore be very carefully followed. To prevent late UE thromboembolism in patients with occluded grafts, the authors strongly advise that such patients undergo a surgical operation with careful follow-up after surgery.

Aged↗