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Biomedical subjects

T Fukui

Publications and source records attributed to T Fukui.

At least 415 records · Page 23Linked to original sources
PubMed1984

Catalytic reaction of glycogen phosphorylase reconstituted with a coenzyme-substrate conjugate.

The role of pyridoxal 5'-phosphate in the catalytic mechanism of glycogen phosphorylase (EC 2.4.1.1) remains unresolved despite extensive investigation. A previous report from this laboratory (Takagi, M., Fukui, T., and Shimomura, S. (1982) Proc. Natl. Acad. Sci. U.S.A. 79, 3716-3719) provided evidence for the direct interaction between the two phosphate groups of the coenzyme and a substrate alpha-D-glucose 1-phosphate. When apophosphorylase is reconstituted with pyridoxal (5')-diphospho(1)-alpha-D-glucose, the enzyme can transfer the glucose moiety to glycogen just as in the normal catalysis. We have studied the kinetics of the glucosyltransfer from this compound to glycogen. The normal and mimic reactions were similar in their kinetic parameters for glycogen and AMP and their activation energies. AMP and other nucleotides that activate the normal reaction could activate the mimic reaction as well. The log k/pH plot for the mimic reaction gave a bell-shaped curve with pKa = 6.90 and pKb = 8.84 at 25 degrees C. The apparent heats of ionization of the corresponding groups having the pKa and pKb were 6.9 and 3.0 kcal/mol, respectively. Reversibility of the glucosyltransfer from the coenzyme-substrate conjugate to glycogen could not be demonstrated, possibly because the equilibrium of this reaction lies further to the polysaccharide synthesis. Based on these and other data which confirm the role of the phosphate group of the coenzyme as an electrophile, we discuss the catalytic mechanism of glycogen phosphorylase. It is suggested that the imidazoyl group of His-376 acts as a nucleophile attacking the anomeric carbon of the substrate glucose 1-phosphate.

Animals↗
PubMed1984

An autopsy case of acute porphyria with a decrease of both uroporphyrinogen I synthetase and ferrochelatase activities.

An autopsy case of a 37-year-old woman with acute porphyria is reported. The patient began to complain of severe menstrual pains, and later developed serious peripheral neuropathy and various autonomic nervous symptoms. The autopsy revealed a marked loss and degeneration of axons and myelin sheaths in the peripheral nervous system (PNS), and prominent central chromatolysis of the spinal anterior horn cells. The predominant process of the peripheral neuropathy appeared to be axonal degeneration. Biochemical analysis showed a marked increase of delta-aminolevulinic acid (ALA), porphobilinogen, uroporphyrin, and coproporphyrin in the urine, and an increase of coproporphyrin and protoporphyrin in the stools and blood. In the analysis of the enzymatic activities of the liver and bone narrow, the activity of ALA synthetase (ALA-S) was markedly increased, and the activities of both uroporphyrinogen I synthetase (URO-S) and ferrochelatase were decreased. It was characteristic in this case that the enzymatic abnormalities found in both acute intermittent porphyria (AIP) and variegate porphyria (VP) coexisted. Biochemical analysis of the sciatic nerve showed an increase of ALA-S activity and a decrease of both URO-S and ALA dehydrase activities. This was the first report that indicated the presence of abnormal activities of the heme biosynthetic enzymes in the peripheral nerves of porphyric patients. The possibility was discussed that these enzymatic abnormalities of the heme biosynthesis in the peripheral nerve itself might be strongly related to the pathogenesis of the porphyric neuropathy.

Adult↗
PubMed1984

Molecular cloning and nucleotide sequence of cDNA coding for rat brain cholecystokinin precursor.

A mixture of 14-mer oligodeoxynucleotides was used for the screening of a cDNA clone coding for a cholecystokinin (CCK) precursor from a cDNA library for rat brain microsomal poly(A)RNA. The longest insert is 718 bp long which was verified to contain a nearly full-length cDNA sequence coding for rat CCK precursor, because the size of CCK mRNA was estimated to be about 850 bases long by Northern blotting analysis. Sequence analysis revealed 110 bp in the 5'-untranslated region, 345 bp in the amino acid coding region corresponding to the CCK precursor and 263 bp in the 3'-noncoding region which contains polyadenylation signal AUUAAA and the poly(A) sequence. The precursor may contain a 28 amino acid signal peptide and 12 additional amino acids at the carboxyl terminus.

Amino Acid Sequence↗
PubMed1983

Isolation and nucleotide sequence of a partial cDNA clone for bovine opsin.

Bovine cDNAs were cloned by using a mixture of 18-base-long synthetic deoxyribonucleotides as a hybridization probe. The longest cDNA clone (pBO-1) contained an 811-bp insert that included the 434 bp of the coding region corresponding to the C-terminal 144 amino acid residues of opsin peptide and the 377 bp of the 3'-untranslated region. The size of opsin mRNA was determined as 23 S by Northern blot hybridization. Bovine liver DNA gave rise to a single band of 2.8 kb, 1.1 kb and 7.9 kb each with Eco RI, Hind III and Bam HI, respectively, by Southern blot hybridization with pBO-1 as probe. Therefore, bovine opsin gene may occur once per haploid genome.

Amino Acid Sequence↗
PubMed1983

An extracellular D(-)-3-hydroxybutyrate oligomer hydrolase from Alcaligenes faecalis.

A strain of Alcaligenes faecalis secretes an extracellular D(-)-3-hydroxybutyrate oligomer hydrolase, in addition to poly(3-hydroxybutyrate) depolymerase, when it is grown in a medium containing poly(3-hydroxybutyrate) as the sole carbon source. The oligomer hydrolase (EC 3.1.1.22), which has been purified to electrophoretic homogeneity, has a molecular weight of 68 000, as estimated by Sephadex G-100 gel filtration, and of 74 000, by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The isoelectric point of the enzyme is approx. 6.0 and the pH optimum for the enzyme reaction is 8.5. The purified oligomer hydrolase has high affinity for oligomeric esters (apparent Km for the D(-)-3-hydroxybutyrate dimer = 32.8 microM; for the dodecamer = 1.3 microM), but does not attack poly(3-hydroxybutyrate) (average molecular weight, 32 500) at all. Analysis of hydrolysates of the oligomeric esters suggests that the enzyme hydrolyzes these substrates from the carboxyl terminus, releasing D(-)-3-hydroxybutyrate units one by one.

Alcaligenes↗
PubMed1983

Antiviral activity of the 3'-amino derivative of (E)-5-(2-bromovinyl)-2'-deoxyuridine.

3'-NH2-BV-dUrd, the 3'-amino derivative of (E)-5-(2-bromovinyl)-2'-deoxyuridine, was found to be a potent and selective inhibitor of herpes simplex virus type 1 (HSV-1) and varicella-zoster virus (VZV) replication. 3'-NH2-BV-dUrd was about 4-12 times less potent but equally selective in its anti-herpes activity as BV-dUrd. Akin to BV-dUrd, 3'-NH2-BV-dUrd was much less inhibitory to herpes simplex virus type 2 than type 1. It was totally inactive against a thymidine kinase-deficient mutant of HSV-1. The 5'-triphosphate of 3'-NH2-BV-dUrd (3'-NH2-BV-dUTP) was evaluated for its inhibitory effects on purified herpes viral and cellular DNA polymerases. Among the DNA polymerases tested, HSV-1 DNA polymerase and DNA polymerase alpha were the most sensitive to inhibition by 3'-NH2-BV-dUTP (Ki values 0.13 and 0.10 microM, respectively). The Km/Ki ratio for DNA polymerase alpha was 47, as compared with 4.6 for HSV-1 DNA polymerase. Thus, the selectivity of 3'-NH2-BV-dUrd as an anti-herpes agent cannot be ascribed to a discriminative effect of its 5'-triphosphate at the DNA polymerase level. This selectivity most probably resides at the thymidine kinase level. 3'-NH2-BV-dUrd would be phosphorylated preferentially by the HSV-1-induced thymidine kinase (Ki 1.9 microM, as compared with greater than 200 microM for the cellular thymidine kinase), and this preferential phosphorylation would confine the further action of the compound to the virus-infected cell.

Antiviral Agents↗
PubMed1983

Maltotriose and maltotetraose excreted in urine following intravenous administration of maltose to human volunteers.

To determine the extent of maltose excreted into the urine, sugar substances present in the urine following intravenous infusion of maltose were analyzed. Maltose, glucose, maltotriose and maltotetraose in the urine were detected by gas chromatography and identified by mass spectrometric analysis. The total amounts of sugar substances excreted after 10 per cent maltose solution given at three different infusion rates were calculated. The excreted amounts of maltotriose and maltotetraose increased in a dose and time dependent manner. As these compounds were not detected in the plasma either during or after the administration of maltose, the kidney probably plays a role in the biosynthesis of maltotriose and maltotetraose. Studies on the organ homogenates of the rabbit showed that the enzyme activity for the biosynthesis of maltotriose from maltose was mainly in the kidney. The glucose excreted into the urine probably originates from maltose catalyzed to glucose, mainly by the action of kidney maltase. As the rate of excretion of sugar substances increased in a dose dependent manner, adequate infusion rates of maltose should be less than 0.5 g/kg/hour.

Adult↗
PubMed1983

The complete nucleotide sequence of the influenza virus neuraminidase gene of A/NJ/8/76 strain and its evolution by segmental duplication and deletion.

The neuraminidase (NA) gene from A/New Jersey (NJ)/8/76 (H1N1, formerly Hsw1 N1) strain isolated in 1976 was cloned into pBR322 and its complete nucleotide sequence was determined. The NJ8 NA gene is 1458 nucleotides long and the sequence predicted the primary structure of the NA molecule comprising of 469 amino acids with a molecular weight of 51,628. Comparison with other NA sequences of the N1 subtype strains which were isolated in 1933-1934 identified the highly variable regions at the amino-terminal stalk region and the carboxy-terminal regions. Potential glycosylation sites encoded by a 15 base-pair unit sequence are arrayed tandemly at the stalk regions. The lengths of stalk regions are highly variable because of segmental deletions in old NA genes. Possible mechanisms for such deletions are discussed.

Animals↗