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Biomedical subjects

S Sugimoto

Publications and source records attributed to S Sugimoto.

At least 235 records · Page 13Linked to original sources
PubMed1979

Two components of chorismate mutase in Brevibacterium flavum.

Chorismate mutase of Brevibacterium flavum, a common enzyme in phenylalanine and tyrosine biosynthesis, was separted into two different component, A and B, with molecular weights of 250,000 and 25,000, respectively, by ammonium sulfate fractionation or gel-filtration. Both components were essential for the enzymatic activity. In the presence of the reaction substrate, chorismate, the two components associated reversibly to give an active enzyme complex with a molecular weight of 320,000. Binding sites of the feedback inhibitors, phenylalanine and tyrosine, on the enzyme were localized on component A as determined by hybridization experiments with the wild-type and mutant components. Tyrosine repressed the synthesis of component B much more strongly than that of component A, while phenylalanine did not show any significant repressive effect on either component. The wild-type strain No. 2247 had four times more component A than component B. Elution patterns in gel, DEAE-cellulose or hydroxyapatite column chromatography as well as the disc-gel electrophoretic pattern of chorismate mutase component A and 3-deoxy-D-arabino-heptulosonate 7-phosphate (DAHP) synthetase activities completely overlapped, suggesting the presence of a bifunctional protein having the two activities. In accord with this suggestion, chorismate mutase as well as DAHP synthetase was insensitive to feedback inhibition by phenylalanine and tyrosine in all the 3-fluorophenylalanine-resistant mutants tested that excreted both phenylalanine and tyrosine. All the phenylalanine and tyrosine double auxotrophs defective in chorismate mutase lacked component B but not A.

Brevibacterium↗
PubMed1977

A simplified method using commercial milk powder for hand-rearing of the Caesarean-derived infant rabbits (author's transl).

An efficient and simplified method for hand-rearing of Caesarean-derived infant rabbits under gnotobiotic condition was devised. The Caesarean-derived infant Dutch or Japanese-White rabbits and their hybrids (F1; Japanese-White female x Dutch male) were reared in sterilized vinyl-isolators by hand-feeding with two kinds of milk diets, A and B, consisted mainly ofa commercial milk powder for dogs and cats (Esbilac) supplemented with several minor components (Table 2) and administered intragastrically once a day through a Nelaton's catheter. Bacteriological examinations revealed that feces and urine were sterile for the first three days. On the third day, Escherichia coli, Staphylococcus epidermidis, Streptococcus faecalis, Bacillus subtilis, Enterococcus, and Bacteroides sp. were given with milk diet and the infant rabbits were reared until 10 to 12 weeks of age. The weaning rate at 5 weeks of age and the raising rate at 3 months of age were approximately 78% and 77%, respectively (Table 3), indicating that feeding once-a-day with a milk diet mainly composed of Esbilac is suitable for the hand-rearing of infant rabbits. There was, however, no significant difference milk diet A and B on the weaning rate.

Animal Feed↗
PubMed1976

Altered prephenate dehydratase in phenylalanine-excreting mutants of Brevibacterium flavum.

The regulatory properties of three key enzymes in the phenylalanine biosynthetic pathway, 3-deoxy-D-arabino-heptulosonate 7-phosphate synthetase (DAHP synthetase) [EC 4.1.2.15], chorismate mutase [EC 5.4.99.5], and prephenate dehydratase [prephenate hydro-lyase (decarboxylating), EC 4.2.1.51] were compared in three phenylalanine-excreting mutants and the wild strain of Brevibacterium flavum. Regulation of DAHP synthetase by phenylalanine and tyrosine in these mutants did not change at all, but the specific activities of the mutant cell extracts increased 1.3- to 2.8-fold, as reported previously (1). Chorismate mutase activities in both the wild and the mutant strains were cumulatively inhibited by phenylalanine and tyrosine and recovered with tryptophan, while the specific activities of the mutants increased 1.3- to 2.8-fold, like those of DAHP synthetase. On the other hand, the specific activities of prephenate dehydratase in the mutant and wild strains were similar, when tyrosine was present. While prephenate dehydratase of the wild strain was inhibited by phenylalanine, tryptophan, and several phenylalanine analogues, the mutant enzymes were not inhibited at all but were activated by these effectors. Tyrosine activated the mutant enzymes much more strongly than the wild-type enzyme: in mutant 221-43, 1 mM tyrosine caused 28-fold activation. Km and the activation constant for tyrosine were slightly altered to a half and 6-fold compared with the wild-type enzyme, respectively, while the activation constants for phenylalanine and tryptophan were 500-fold higher than the respective inhibition constants of the wild-type enzyme. The molecular weight of the mutant enzyme was estimated to be 1.2 x 10(5), a half of that of the wild-type enzyme. The molecular weight of the mutant enzyme was estimated to be 1.2 X 10(5) a half of that of the wild type enzyme, while in the presence of tyrosine, phenylalanine, or tryptophan, it increased to that of the wild-type enzyme. Immediately after the mutant enzyme had been activated by tyrosine and then the tyrosine removed, it still showed about 10-fold higher specific activity than before the activation by tyrosine. However, on standing in ice the activity gradually fell to the initial level before the activation by tyrosine. Ammonium sulfate promoted the decrease of the activity. On the basis of these results, regulatory mechanisms for phenylalanine biosynthesis in vivo as well as mechanisms for the phenylalanine overproduction in the mutants are discussed.

3-Deoxy-7-Phosphoheptulonate Synthase↗
PubMed1976

Effect of prolonged administration of clonidine to spontaneously hypertensive rats on blood pressure, cerebral norpinephrine content and angiographic finding in the kidney.

1. The effects of clonidine on blood pressure, cerebral norepinephrine content and vascular structures of the kidneys were investigated in 21 SHR. Although the body weight was not affected by long term clonidine treatment up to 36 weeks, the syatolic blood pressure was significantly reduced. The reduction of the blood pressure was already obvious after 1 week administration of clonidine but the effect was more prominent after long term treatment of 30 weeks or longer. 2. The cerebral norepinephrine content was significantly lower in SHR, regardless of with or without clonidine treatment, than in the control Wistar rats. Although the cerebral norepinephrine content was slightly increased following clonidine treatment SHR, the increase was not statistically significant. 3. Angiographic study of the kidneys revealed a poor opacification of the blood vessels and glomeruli in SHR compared with the control Wistar rats. There was no difference in the sizes of the arcuate and interlobular arteries in SHR and the control Wistar rats, although the medial muscular hypertrophy of the arteries was slightly more prominent in the SHR histologically. The more prominent in the SHR histologically. The angiographic and histologic findings of the renal arteries were not altered following long term clonidine treatment. A possibility was considered that the renal arterioles are mainly functionally affected in SHR.

Animals↗