Kei Sasaoka

Occurrence of a new enzyme catalyzing the direct conversion of NG,NG-dimethyl-L-arginine to L-citrulline in rats.

An enzyme concerned with the degradation of NG,NG-dimethyl-L-arginine to L-citrulline was investigated in rats. The enzyme purified from rat kidney catalyzed the direct conversion of NG,NG-dimethyl-L-arginine to L-citrulline with liberation of dimethylamine from the methylated guanidino moiety. The reaction required no co-factor and the maximum activity was obtained at pH 6.5. The enzyme was highly specific for NG,NG-dimethyl-L-arginine.

Occurrence of D-amino acid aminotransferase in pea seedlings

Abstract Aminotransferase reacting between D-amino acids and α-keto acids was found in the germinating pea seedlings. With partial purification, it was evident that the enzyme preparation contained no racemase and L-amino acid aminotransferase and was only specific for D-amino acid transamination. Large amounts of D-alanine found in the germinating pea seedlings were assumed to be formed by this enzyme action.

d-Alanine in germinating Pisum sativum seedlings

Abstract Germinating pea seedlings ( Pisum sativum var. Alaska) contain high concentrations of d -alanine, which occurs in the decotyledonized parts as the conjugates, N -malonyl- d -alanine and γ- l -glutamyl- d -alanine. By contrast, free alanine in pea seedlings is almost all l -isomer. During early stages of the germination, γ- l -glutamyl- d -alanine increased significantly and amounted to ca. 2.5 μmol/seedling at 8 days.

Antivitamin B-6 effect of 1-aminoproline on rats

By intraperitoneal injection of 1-aminoproline, death after severe convulsion was observed in rats (LD50 of 1-amino-L-proline, 26 mg per kg of body weight for young male rats fed a normal diet). The vitamin B-6-deficient rats were more sensitive to this hydrazino acid than the normal rats. The toxic effect was completely prevented by the administration of pyridoxine. 1-Amino-D-proline was less toxic than the L-isomer. By the 1-aminoproline treatment, the most remarkable changes in the free amino acid levels were the striking increases in the concentrations of alpha-aminoadipic acid, citrulline and cystathionine in all the tissues tested, except in brain. Some unidentified ninhydrin-positive substances appeared. These results indicate that 1-aminoproline greatly disturbed the amino acid pattern, i.e. the amino acid metabolism in rats.

Incorporation of radioactive shikimic acid into N-(γ-Lglutamyl)-4-hydroxyaniline in Agaricus bisporus

Abstract Agaricus bisporus contains novel aromatic compounds. By incubation of the mushroom with [G- 14 C] shikimic acid, the radioactivity was incorporated into tyrosine, phenylalanine and several unidentified metabolites. The most radioactive metabolite in the stipe and the cap was identified as N-(γ- L -glutamyl )-4- hyrroxyaniline . The radioactivity was proved to be localized in the 4-hydroxyaniline moiety of this compound.

De novo synthesis of d-alanine in germinating Pisum sativum seedlings

Abstract The amounts of d -alanine derivatives, γ- l -glutamyl- d -alanine and N -malonyl- d -alanine, increase rapidly during the early growth of pea seeds. Pyruvate-[1− 14 C], l -alanine-[U− 14 C], d -alanine-[U− 14 C], l -alanine-[ 15 N] and 15 NH 4 Cl were therefore fed to the seedlings and the incorporation investigated. Labelling results revealed that pea seedlings can utilize these erogenous compounds to form d -alanine and that labelled l -alanine is effectively converted to the d -enantiomer with retention of 14 C and, largely, 15 N label. Enzyme analyses in vitro provided additional evidence that the extract of pea seedlings catalyzes the direct conversion of l -alanine to d -alanine. The data suggest that the de novo synthesis of d -alanine in pea seedlings occurs by a racemase reaction.

Studies on the biosynthesis of N-(γ-L-glutamyl)-4-hydroxyaniline] in Agaricus bisporus: Identification of the position in shikimic acid at which the amination occurs

Abstract Labelled shikimic acid was efficiently incorporated into the aniline moiety of N-(γ- L - glutamyl )-4- hydroxyaniline , a characteristic aromatic compound of the common mushroom, Agaricus bisporus. Incubations with [3-3H]- and [1,6-14C]shikimic acid clearly proved that the amination of shikimic acid occurs at its 4-position during the biosynthesis of N-(γ- L - glutamyl )-4- hydroxyaniline .

γ-glutamyl-β-cyanoalanylglycine, a metabolite of β-cyanoalanine in the rat and chick☆

Abstract The young rat or chick fed β-cyanoalanine accumulates in certain tissues a new substance which has been isolated in crystalline form and identified chemically as γ-glutamyl-β-cyanoalanylglycine. The chick accumulates, in addition, γ-glutamyl-β-cyanoalanine. The presence of bound β-cyanoalanine in the two metabolites was confirmed by enzymatic liberation of free β-cyanoalanine. The findings may provide insight into the etiology of some of the γ-glutamyl oligopeptides present in animal tissue.

Incorporation of chorismic acid and 4-aminobenzoic acid into the 4-hydroxyaniline moiety of N-(γ-L-glutamyl)-4-hydroxyaniline in Agaricusbisporus

Agaricus bisporus contains the unique aniline derivative, N-(gamma-L-glutamyl)-4-hydroxyaniline. 14C-labelled chorismic acid was quantitatively incorporated into the 4-hydroxyaniline moiety of this aniline derivative, whereas 14C-labelled prephenic acid and anthranilic acid were not incorporated into 4-hydroxyaniline. These observations indicate the branch point of the biosynthetic route of 4-hydroxyaniline in the shikimic acid pathway to be chorismic acid. Moreover, 4-aminobenzoic acid proved to be an effective precursor of 4-hydroxyaniline.

ds-erythro-2-amino-3,4-dihydroxybutanoic acid, a constituent in the edible mushroom, lyophyllum ulmarium

Abstract An unusual amino acid occurring in the fruiting bodies of Lyophyllum ulmarium was identified as d s - erythro - 2-amino-3,4-dihydroxybutanoic acid, which is a compound found for the first time in biological materials.