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S Sano

Publications and source records attributed to S Sano.

At least 271 records · Page 15Linked to original sources
PubMed1981

Evidence of increased synthesis of delta-aminolevulinic acid dehydratase in experimental lead-poisoned rats.

delta-Aminolevulinic acid dehydratase (porphobilinogen synthase; 5-aminolevulinate hydro-lyase, EC 4.2.1.24) was purified from rat and rabbit erythrocytes to a homogeneous state. Specific activities were 26.0 and 26.6 units/mg protein for the rat and rabbit enzymes, respectively, and their estimated molecular weight was 280000, each consisting of 8 subunits of Mr 35000. In order to quantitate rat delta-aminolevulinic acid dehydratase at several stages of lead-poisoning, a radioimmunoassay technique using goat antiserum against the rat enzyme was developed for the first time. This technique was specific, reproducible and highly sensitive allowing determination of ng enzyme. When drinking water containing 25 mM lead acetate was given daily to rats ad lib. the delta-aminolevulinic acid dehydratase activity in the blood, assayed without any pretreatment, decreased to 8% of the control level on the next day. On the contrary, the restored enzyme activity, assayed in the presence of Zn2+ and dithiothreitol, was greater than normal by the fourth day of lead administration in bone-marrow cells and by the ninth day in the peripheral blood. The increased activity level stayed the same from the ninth day onward. The enzyme content as determined directly by the radioimmunoassay technique at this stage was about 2-fold above that the control. There was no significant difference in the number of reticulocytes and the distribution profile of different types of reticulocytes between the lead-exposed and non-exposed rats. Therefore, the increase in the amount of delta-aminolevulinic acid dehydratase in erythrocytes of lead-poisoned rats was suggested to be due to an increased rate of synthesis in the bone-marrow cells.

Animals↗
PubMed1981

Degradation of mesoheme and hydroxymesoheme catalyzed by the heme oxygenase system: involvement of hydroxyheme in the sequence of heme catabolism.

Mesoheme bound to heme oxygenase protein was easily degraded to mesobiliverdin by incubation with NADPH-cytochrome c reductase and NADPH. The features of mesoheme degradation were very similar to those of protoheme degradation catalyzed by the heme oxygenase system; an intermediate compound having its absorption maximum at 660 nm appeared in the couse of mesoheme degradation and this compound is presumably equivalent to the 688 nm compound which appears in the course of protoheme degradation. Hydroxymesoheme was chemically prepared and a complex of hydroxymesoheme and heme oxygenase was prepared. The complex was fairly stable in air, but when the complex was incubated with the NADPH-cytochrome c reductase system, the hydroxymesoheme bound to heme oxygenase was readily converted to mesobiliverdin through the 660 nm compound as an intermediate. It is evident that hydroxyheme is a real intermediate of heme degradation in the heme oxygenase reaction and that the 688 nm compound (or the 660 nm compound in the mesoheme system) is located between hydroxyheme and the biliverdin-iron chelate. The ferrous state of heme-iron may also be necessary for the onset of further oxidation of hydroxyheme.

Animals↗
PubMed1981

pH dependence of the binding constant of Ca2+ to the phospholipase A2 of A. halys blomhoffii. Participation of ionizable groups with pK values of 5.16, 6.45, and 7.30.

The pH dependence of the binding constant of Ca2+ to the phospholipase A2 of A. halys blomhoffii was studied at 25 degrees C and an ionic strength of 0.1 by the tryptophyl fluorescence method and aromatic circular dichroism (Ikeda and Samejima (1981) J. Biochem. 89, 1175-1184), and was compared with those for cobra venom phospholipases A2 (Teshima et al. (1981) J. Biochem. 89, 13-20) and for porcine pancreatic enzyme (Pieterson et al. (1974) Biochemistry 13, 1439-1445). The shape of the pH-dependence curve was closer to that for the porcine enzyme than those for the cobra enzymes. The data were analyzed on the basis of our previous findings (Ikeda and Samejima (1981) J. Biochem., 90, 799-804) that the pK value of the ionizable group (alpha-amino group) is perturbed from 7.30 to 6.30 on the Ca2+ binding, and that the protonation of another group corresponding to Asp 49 of the porcine enzyme with a pK value of 5.16 competes with the Ca2+ binding. An additional ionizable group with a pK value of 6.45 was found to participate in the Ca2+ ion binding, and this was assigned to the His residue corresponding to His 48 in the active site of the porcine enzyme.

Calcium↗
PubMed1980

Coproporphyrinogen oxidase. I. Purification, properties, and activation by phospholipids.

Coproporphyrinogen oxidase (EC 1.3.3.3), which converts coproporphyrinogen III into protoporphyrinogen IX, was purified about 3,200-fold from bovine liver. The most purified preparation had a specific activity of 6,920 units/mg of protein, the highest value so far reported, and was homogeneous in the polyacrylamide gel electrophoresis. The enzyme was monomeric and its molecular weight was approximately 71,600. The purified enzyme was analyzed for the amino acid composition and shown to have an abundance of aromatic amino acid residues amounting to 12% of the total residues. Spectral examination did not reveal the presence of heme and flavin. No metals were detected by atomic absorption spectroscopy either. Sulfhydryl reagents, metals, and metal chelators did not affect the enzyme activity to any significant extent. On the contrary, the purified enzyme was activated by crude phospholipid extracts from liver mitochondria and commercially available phospholipids about 2- to 5-fold. An increase in Vmax by the phospholipid extract as well as phosphatidylethanolamine accompanied a decrease in Km for coproporphyrinogen III from 48 microM to 18 to 25 microM. Synthetic nonionic detergents also exhibited an activation effect, although ionic detergents diminished the activity.

Amino Acids↗
PubMed1980

Coproporphyrinogen oxidase. II. Reaction mechanism and role of tyrosine residues on the activity.

Purified coproporphyrinogen oxidase catalyzed conversion of 2-beta-hydroxypropionic acid-4-propionic acid deuteroporphyrinogen IX, 2-propionic acid-4-beta-hydroxypropionic acid deuteroporphyrinogen IX, 2,4-bis (beta-hydroxypropionic acid) deuteroporphyrinogen IX, harderoporphyrinogen, and isoharderoporphyrinogen to protoporphyrinogen IX. This result suggests that the enzymatic conversion of propionate groups of coproporphyrinogen III to vinyl groups of protoporphyrinogen IX occurs stepwise starting from position 2 to 4 through beta-hydroxypropionate porphyrinogen as an intermediate. When coproporphyrinogen oxidase was treated with tetranitromethane, an initial modification of 1 tyrosine residue per molecule did not affect the enzyme activity, whereas modification of a second tyrosine residue resulted in a substantial inactivation of the enzyme. Conversion of 2,4-bis-(beta-hydroxypropionic acid) deuteroporphyrinogen XI into protoporphyrinogen IX was not affected by the tyrosine residue modification. Both modification and kinetic studies led to a conclusion that at least one tyrosine residue is involved in the active site of the enzyme, presumably participating in the initial reaction of the oxidation step of a propionate group to beta-hydroxypropionate.

Aerobiosis↗