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Biomedical subjects

K Asada

Publications and source records attributed to K Asada.

At least 163 records · Page 9Linked to original sources
PubMed1986

Amino acid sequence of copper,zinc-superoxide dismutase from spinach leaves.

The complete amino acid sequence of Cu,Zn-superoxide dismutase (SOD) from spinach leaves has been determined on the basis of peptides obtained by cyanogen bromide (BrCN) cleavage and by enzymic hydrolyses with Achromobacter lyticus lysylendopeptidase, Staphylococcus aureus V8 protease, trypsin, and thermolysin. The spinach SOD consists of a total of 154 amino acid residues with alanine as the amino(N)-terminus and valine as the carboxy(C-)terminus. The present sequence, which has been established for the enzyme from a plant, is also highly homologous to those of the enzymes from other species. Especially, the residues essential for metal binding and enzyme activity have been extensively conserved among all of the Cu,Zn-SODs hitherto analyzed.

Acetylation↗
PubMed1985

Monodehydroascorbate reductase from cucumber is a flavin adenine dinucleotide enzyme.

Monodehydroascorbate reductase (EC 1.6.5.4) was purified from cucumber fruit to a homogeneous state as judged by polyacrylamide gel electrophoresis. The cucumber monodehydroascorbate reductase was a monomer with a molecular weight of 47,000. It contained 1 mol of FAD/mol of enzyme which was reduced by NAD(P)H and reoxidized by monodehydroascorbate. The enzyme had an exposed thiol group whose blockage with thiol reagents inhibited the electron transfer from NAD(P)H to the enzyme FAD. Both NADH and NADPH served as electron donors with Km values of 4.6 and 23 microM, respectively, and Vmax of 200 mol of NADH and 150 mol of NADPH oxidized mol of enzyme-1 s-1. The Km for monodehydroascorbate was 1.4 microM. The amino acid composition of the enzyme is presented. In addition to monodehydroascorbate, the enzyme catalyzed the reduction of ferricyanide and 2,6-dichloroindophenol but showed little reactivity with calf liver cytochrome b5 and horse heart cytochrome c. The kinetic data suggested a ping-pong mechanism for the monodehydroascorbate reductase-catalyzed reaction. Cucumber monodehydroascorbate reductase occurs in soluble form and can be distinguished from NADPH dehydrogenase, NADH dehydrogenase, DT diaphorase, microsome-bound NADH-cytochrome b5 reductase, and NADPH-cytochrome c reductase by its molecular weight, amino acid composition, and specificity of electron acceptors and donors.

Amino Acids↗
PubMed1985

Molecular orientation of plastocyanin on spinach thylakoid membranes as determined by acetylation of lysine residues.

To reveal the molecular orientation of plastocyanin (PC) on spinach thylakoid membranes, the position of Lys residues modified by acetic anhydride was compared between thylakoid-bound PC and the isolated one. Digestion of the isolated PC by a trypsin yielded a peptide map with seven spots prior to the acetylation of the protein; none of the spots appeared after the isolated PC was acetylated. On the other hand, there were two spots on the peptide map of the PC acetylated when it was bound to the thylakoids. Those spots were revealed by their amino acid compositions to correspond to the peptide fragments Phe 82-Lys 95 and Val 96-Asn 99. Thus, the Lys residues 81 and 95 of the thylakoid-bound PC were not acetylated. These results suggest that the PC molecule binds to the thylakoids with a specific region including the Lys's 81 and 95 in contact with the membranes. The Lys's 81 and 95 are located near Tyr 83, which has been thought to be the delivery site of electrons from the Cu2+ center.

Acetylation↗
PubMed1985

Cloning of the contiguous 165-kilobase-pair region around the terminus of Escherichia coli K-12 DNA replication.

Escherichia coli K-12 chromosomal DNA was partially digested with either EcoRI or HindIII, and cosmid libraries were constructed. By screening these libraries, a series of partially overlapping clones which covered the terC region was isolated. The cloned area spanned about 165 kilobase pairs, corresponding to the 29.7-to-33.2-min region of the genetic map of the E. coli chromosome.

Chromosome Mapping↗
PubMed1984

Correlation between dose and tumor response in the radiotherapy of lung cancer of various histological types.

Correlation between dose and tumor response by cell types was determined in 50 patients with lung cancer in order to predict the possibility of further tumor regression. The TDF (time-dose-fractionation) concept was used as dose factor. The radiation source was a cobalt-60 gamma-ray or linear accelerator 10 MV X-ray. As a routine regime a fraction dose of 2 Gy five times per week was given to 39 of the 50 patients, but a dose of 2 Gy three times per week or of 1.5 Gy five times per week was given to seven and four patients, respectively. Radiation response was the best in small cell carcinoma and better in adenocarcinoma than in squamous cell carcinoma, showing a tumor regression rate of 50% or more in 90%, 80% and 58% of the patients, respectively. The correlation between tumor regression rate and TDF values was good in squamous cell carcinoma (r = 0.73) and small cell carcinoma (r = -0.72), but poor in adenocarcinoma (r = -0.10). These results suggest that in squamous cell carcinoma improvement of tumor regression can be expected by increasing TDF values, and in adenocarcinoma and small cell carcinoma the optimal TDF values are about 100 and 60 to 80, respectively.

Adenocarcinoma↗