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T Yamano

Publications and source records attributed to T Yamano.

At least 307 records · Page 17Linked to original sources
PubMed1976

Interaction between D-amino acid oxidase and small molecules.

1. From the standpoint of monomer-dimer equilibrium of hog kidney D-amino acid oxidase [EC 1.4.3.3] and the interaction between the enzyme and small molecules, the effect of pH on the binding of p-aminobenzoate to the monomer and dimer of the enzyme was studied by kinetic methods and spectrophotometric titration. 2. The maximum binding number of p-aminobenzoate to the dimer is two molecules, and there is no interaction between the two active sites of the dimer (i.e., no cooperativity) over the range of pH from 6.5 to 10. 3. The affinity of the dimer for p-aminobenzoate is several times higher than that of the monomer at pH 6.5-10, and consequently p-aminobenzoate induces dimerization in the equilibrium state of D-amino acid oxidase. The interaction energy of two subunits of the dimer is stabilized by the binding of p-aminobenzoate by 1-2 kcal/mole over the pH range studied. 4. The binding sites of the quasi-substrate, p-aminobenzoate, in the dimer and the intersubunit binding site of the dimer are clearly different, because p-aminobenzoate induces dimerization of the enzyme. 5. The pK values of ionizing groups in the free monomer and the free dimer which participate in the binding of the competitive inhibitor, p-aminobenzoate, are approximately the same, 8.7, as determined from the pH dependence of the affinity of the inhibitor for the enzyme. Furthermore, no pK for the enzyme-inhibitor complex in the pH range 6.5-10 was observed. 6. There is no interaction between the two ionizing groups of the dimer during protonation-deprotonation, because a theoretical equation involving no cooperativity between the two ionizing groups in the dimer explains the results well.

4-Aminobenzoic Acid↗
PubMed1976

A study of the interaction between D-amino acid oxidase and quasi-substrates.

To study the interaction between D-amino acid oxidase [EC 1.4.3.3] and quasi-substrates such as benzoate and o-, m-, and p-aminobenzoate, visible circular dichroism spectra (CD spectra) were measured and the binding rate and affinity of o-aminobenzoate to the enzyme were observed by following the absorption changes at various wavelengths. We found a new CD band around 560 nm, corresponding to the charge-transfer complexes which result from the formation of aminobenzoate complexes with the enzyme. The ellipticity of this band was positive for the p-aminobenzoate complex, but negative for the o- and m-aminobenzoate complexes. Crossover points in CD spectra were observed at 470 nm for the m-aminobenzoate complex and at 475 nm for the o-aminobenzoate complex. They probably resulted from overlapping of the positive CD band of FAD bound with the enzyme and the negative CD band of the charge-transfer complex. We propose that the amino group in aminobenzoate, not the pi-electrons of the benzene ring, is the electron donor in the charge-transfer complex and that the position of the amino group is very important for the charge-transfer interaction. The binding rate and affinity of o-aminobenzoate to the enzyme were determined using the absorption changes at 370 nm (380 nm), caused by the modification of electronic states of FAD bound with the enzyme, and at 550 nm (565 nm), caused by the formation of the charge-transfer complex of o-aminobenzoate with the enzyme. No differences between these parameters with wavelength were observed. This independence of wavelength simplifies discussion of the experimental data obtained from absorption changes.

Aminobenzoates↗
PubMed1976

Inhibition of coliphage multiplication and R plasmid transfer by desdanine.

Desdanine inhibited the plaque formation of male-specific coliphages but not that of other coliphages tested. Desdanine also suppressed the multiplication of both RNA phage Q beta and filamentous DNA phage f1 at the concentration of 3.13 approximately 6.25 mug/ml which had no influence on the growth of their host cells. However, the inhibitory effect on the phage multiplication was not due to the inactivation of phage particles nor the prevention of phage adsorption and penetration into the host cells. Desdanine also inhibited the transfer of R plasmid, R 100-1, in E. coli at 6.25 approximately 12.5 mug/ml without affecting the viability of donor and recipient cells.

Acrylamides↗
PubMed1976

Change in the mixed function oxidase system of liver microsomes in rats treated with 3'-methyl-4-dimethylaminoazobenzene.

The mixed function oxidase systems of plasma membranes, the Golgi apparatus, and smooth and rough endoplasmic reticula of the livers of rats fed on a standard diet containing 0.06% (w/w) 3'-methyl-4-dimethylaminoazobenzene were investigated. The components and activities of the mixed function oxidase systems of the smooth endoplasmic reticulum and Golgi apparatus were especially reduced by the carcinogen. The activities for hydroxylation of anilines and demethylation of p-nitroanisole and the contents of cytochromes P-450 and b5 of the submicrosomal fractions of the rats decreased considerably more than the activities of NADH- and NADPH-ferricyanide reductases. More than 90% of the ferri-cytochrome P-450 content of the 3'-methyl-4-dimethylaminoazobenzene induced microsomes at 20 K was in the low spin form.

Administration, Oral↗
PubMed1975

Stoichiometry of 4-methyl sterol oxidase of rat liver microsomes.

The stoichiometry of 4-methyl sterol oxidase has been investigated by concurrent assays of rates of oxygen consumption, oxidation of reduced pyridine nucleotide, and formation of steroid 4alpha-oic acid, which is the oxidized product of attack of 4-methyl sterol precursors of cholesterol. The basal, steroid-independent rates of oxidation of alpha-NADH and alpha-NADH-dependent oxygen consumption by rat liver microsomes are about 10 to 15% of the rates observed with beta-NADH. Thus, alpha-NADH is substituted for beta-NADH; alpha-NADH oxidation is observed spectrophotometrically. The slow rate of oxygen consumption is measured accurately with a galvanic oxygen electrode that is attached to an offset amplifier. For maximal velocity, 4alpha-hydroxymethyl-5alpha-cholest-7-en-3beta-ol is the steroid substrate, and oxidase activity is induced 2-fold with a dietary bile acid sequestrant. Under these conditions, accurate measurements are obtained for substrate-dependent increments, which are equal to or greater than basal, substrate-independent rates. For each equivalent of hydroxymethyl group oxidized to carboxylic acid, 2 eq each of oxygen and alpha-NADH are consumed. Thus, the stoichiometry is consistent with that expected for two sequential attacks of the 4alpha-hydroxymethyl group by an external mixed function oxidase. In addition to establishing the stoichiometry of the 4-methyl sterol oxidase, the results further demonstrate that the steroidal 4alpha-carboxylic acid is formed from the hydroxymethyl intermediate by catalysis of a mixed function oxidase rather than dehydrogenases.

Animals↗
PubMed1975

Antithyroid antibodies in Alport's syndrome.

Two families in which more than two members had Alport's syndrome were examined. Serum-antithyroid-antibodies were found in all those with Alport's syndrome and some of their relatives. These included three cases of Alport's syndrome with nephritis and/or nerve deafness and two normal people who can be regarded as carriers of Alport's syndrome from one family, and one case of the syndrome with nephritis and deafness from the other family. One case of Alport's syndrome had symptoms of hypothyroidism, and biopsy specimens from another case were characteristic of chronic thyroiditis. The results indicate that serum-anti-thyroidantibodies, together with nephritis and deafness, are a sign of Alport's syndrome. The results accord with transmission of the syndrome as an autosomal dominant trait and suggest that Alport's syndrome may be caused by an immunological abnormality.

Adolescent↗
PubMed1975

Effects of cyanide on stearyl-coenzyme A desaturase activities in microsomes from various mammalian tissues.

The effect of potassium cyanide on the desaturase activity for stearyl-CoA in microsomes of various mammalian tissues has been investigated. Potassium cyanide inhibited the desaturase activities in microsomes from livers of rat, hen, guinea pig and rat lung, but not the activities in microsomes from rabbit liver, pig thyroid and bovine adrenocortex, It is concluded that the so-called "cyanide-sensitive factor" does not seem to be common to all the desaturase activities of stearyl-CoA in the microsomes of mammalian tissues.

Adrenal Cortex↗
PubMed1975

Microbial transformation of validamycins.

Alpha- or beta-Glucosidic linkage of validamycin was selectively cleaved by microbial hydrolysis and especially the conversion of validamycin C into validamycin A by the selective hydrolysis of alpha-glucoside linkage has important significance because validamycin C is considerably less active than validamycin A. Semisyntheses of validamycins including a new validamycin, beta-D-galactosyl-validoxylamine A were carried out by microbial transglycosidation using validoxylamine A as a glycosyl acceptor. D-[U-14C]glucose and [14C]validoxylamine A were highly incorporated into validamycin A by validamycin-producing Streptomyces hygroscopicus var. limoneus.

Aminoglycosides↗
PubMed1975

Affinity labeling of D-amino acid oxidase with an acetylenic substrate.

The acetylenic substrate, D-2-amino-4-pentynoic acid (D-propargylglycine), was oxidatively deaminated by hog kidney D-amino acid oxidase[EC 1.4.3.3], with accompanying inactivation of the enzyme. The flavin which was extracted by hot methanol from the inactivated enzyme was identical with authentic FAD by thin-layer chromatography and circular dichroism. The excitation spectrum of emission at 520 nm of the released flavin was very similar to the absorption spectrum of oxidized FAD. The released flavin was reduced by potassium borohydride. The apoenzyme prepared after propargylglycine treatment did not show restored D-amino acid oxidase activity on adding exogenous FAD. The absorption spectrum of this inactivated apoenzyme showed absorption peaks at 279 and 317 nm, and a shoulder at about 290 nm. These results strongly indicate that the inactivation reaction is a dynamic affinity labeling with D-propargylglycine which produces irreversible inactivation of the enzyme by a covalent modification of an amino acid residue at the active site.

Affinity Labels↗