PubMed Health⌕ Search

Biomedical subjects

T Amachi

Publications and source records attributed to T Amachi.

45 records · Page 3Linked to original sources
PubMed1990

Luminol chemiluminescence reaction catalyzed by a microbial peroxidase.

A peroxidase produced by microorganisms belonging to the genera Arthromyces and Coprinus was found to be a potent catalyst for the chemiluminescent oxidation of luminol, the luminescence produced per unit of microbial peroxidase protein being well over 100 times as strong as that produced by horseradish peroxidase. No large difference in Km value for H2O2 in the presence of luminol was found between Arthromyces ramosus peroxidase and horseradish peroxidase (7.0 and 15.5 microM, respectively), but Vmax of the Arthromyces peroxidase was 500 times greater than that of the horseradish peroxidase. It was also found that the Arthromyces peroxidase surpasses, beyond expectation, the horseradish peroxidase in the initial velocity of the chemiluminescence reaction with the stopped-flow method. The Arthromyces peroxidase was used for the glucose and cholesterol assays, which were notably more sensitive than the corresponding assays involving the horseradish peroxidase.

Calibration↗
PubMed1990

Site-directedly mutated human cytochrome c which retains heme c via only one thioether bond.

Although Cys-14 (human numbering) of cytochrome c was conserved during its molecular evolution and it is supposed to be essential for most cytochromes c to retain heme c via two thioether bonds, a site-directedly mutated human cytochrome c which has an alanine residue at this position and only one thioether bond through Cys-17 turns out to be functional. This shows that Cys-14 is not essential. The absorption spectrum of the atypical cytochrome c is red shifted, and similar to those of Euglena and Crithidia cytochromes c, which also have only one thioether bond [Pettigrew, G.W., Leaver, J.L., Meyer, T.E., & Ryle, A.P. (1975) Biochem. J. 147, 291-302].

Amino Acid Sequence↗
PubMed1990

High-level secretion of a Rhizopus niveus aspartic proteinase in Saccharomyces cerevisiae.

The gene encoding an extracellular Rhizopus niveus aspartic proteinase I (RNAP-I) was introduced into Saccharomyces cerevisiae. The yeast cell carrying a plasmid containing the intact RNAP-I gene under the control of the glyceraldehyde 3-phosphate dehydrogenase (GAPDH) gene promoter of S. cerevisiae did not synthesize RNAP-I at all. On the other hand, when the intron of the RNAP-I gene had been removed from the gene in the plasmid, the cell secreted RNAP-I with high efficiency. Processing of the pro-sequence occurred at the same region of the pro-enzyme during cultivation as observed in the culture of R. niveus. Moreover, the promoter and the terminator of the original RNAP-I gene were found to be weakly functional in the yeast cell with respect to expression of the intronless RNAP-I gene, although the initiation and termination sites were heterogeneous. The effects of vector-types on the extracellular production of RNAP-I were also investigated.

Aspartic Acid Endopeptidases↗
PubMed1988

Construction of a human cytochrome c gene and its functional expression in Saccharomyces cerevisiae.

The nucleotide sequences of a partial cDNA and three pseudogenes of human cytochrome c were determined. The complete nucleotide sequences which encode human cytochrome c were constructed on the basis of one of the pseudogenes by in vitro mutagenesis. The constructed human cytochrome c was functionally expressed in Saccharomyces cerevisiae. The recombinant human cytochrome c was purified and characterized.

Base Sequence↗
PubMed1988

Amino acid replacement studies of human cytochrome c by a complementation system using CYC1 deficient yeast.

Various in vitro mutated human cytochrome c genes which encode displaced amino acid residues at the 14th, 17th, 28th, 37th, 38th, 56th, and/or 84th residues were constructed, and their degrees of complementation of yeast CYC1 deficiency were examined. Invariant Cys-17 and Arg-38 could not be replaced by alanine and tryptophan, respectively, without function impairment. Cytochrome c containing Ala-14 instead of conserved Cys-14, Gly-38 or Lys-38 instead of Arg-38, and Ser-84 instead of invariant Gly-84 were partly functional. These results indicate that these invariant or conserved residues are important. Cytochromes c containing Cys-56 instead of native Gly-56 was partly functional. Cytochrome c containing Arg-37 and Gly-38 instead of Gly-37 and Arg-38 was slightly functional. Replacement of variable Thr-28 and Gly-37 by Ile-28 and Arg-37, respectively, produced no effects. Our results are as a whole consistent with the view that conserved residues are important and variable residues are less important for cytochrome c to function.

Amino Acids↗
PubMedDate not supplied

Isolation from beer and structural determination of a potent stimulant of gastrin release.

Beer was subjected to five successive chromatographic procedures to isolate the gastrin release-inducing activity, guided by bioassay of the fractions in anaesthetized Donryu rats. The procedures were: (1) hydrophobic interaction chromatography (aqueous effluent with an HP20 column); (2) weak cation-exchange chromatography (1 M acetic acid eluate with a CM Sephadex C-25 column); (3) gel filtration (methanol eluate with a Sephadex LH-20 column); (4) same as (2); (5) high-performance liquid chromatography (YMC-Pack ODS-AM with 7% acetonitrile-0.01 M HCl). The active component finally isolated had a specific activity approximately 10000 times higher than that of beer. It was identified by means of mass, 1H- and 13C-nuclear magnetic resonance spectral analyses as N-methyltyramine (NMT). The dose of NMT giving maximal gastrin-releasing activity was 25 microg/kg, and the 50% effective dose was approximately 10 microg/kg on oral administration to rats. NMT was isolated and identified as a gastrin release inducer in beer. Its concentration in beer is sufficient to account for most of the activity of beer.

Adrenergic alpha-Agonists↗