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Biomedical subjects

K Arima

Publications and source records attributed to K Arima.

At least 253 records · Page 14Linked to original sources
PubMed1975

Studies on sulfhydryl groups of Aspergillus niger amine oxidase.

Amino acid analysis of the amine oxidase of Aspergillus niger (monoamine:O2 oxidoreductase (deaminating), EC 1.4.3.4) showed a composition similar to that of bovine plasma enzyme. One molecule of enzyme contained 25 Cys residues. It was shown that 9 to 11 residues of Cys were titrated to be SH groups. The amine oxidase reaction was markedly inhibited by metal ions (Cu2+, Hg2+, Ag+). The enzyme was inactivated with SH reagents (phenyl mercuric acetate, Cl-HgBzO-) and the extent of this inactivation was dependent on the time of incubation with SH reagents. Also, the Cl-HgBzO- -inactivated enzyme was reactivated with cysteine and this reactivation was biphasic with the time of incubation. The Cl-HgBzO--inactivated amine oxidase was compared with the native enzyme in their reactivity with phenylhydrazine and their spectral properties. The results showed that the Cl-HgBzO--inactivated enzyme had lower reactivity with phenylhydrazine than the native enzyme and had higher absorbance values than the native enzyme around 400 nm wavelengths.

Amino Acids↗
PubMed1975

Studies on NADP-+-specific isocitrate dehydrogenase from an extreme thermophile, Thermus flavus AT-62.

1. NADP-+-specific isocitrate dehydrogenase [EC 1.1.1.42] was partially purified by about 440-fold from an extreme thermophile, Thermus flavus AT-62. 2. Remarkable thermostability of the enzyme was confirmed. The enzyme was not inactivated after 60 min at 70 degrees, and the activity was lost only slowly at 80 degrees. Above 90 degrees, however, rapid inactivation was observed. 3. The dehydrogenase was susceptible to concerted inhibition by oxaloacetate plus glyoxylate. In the presence of oxaloacetate plus glyoxylate (each 1 mM), 75 percent inhibition was observed. 4. The degree of inhibition of the enzyme by oxaloacetate plus glyoxylate decreased markedly above 60 degrees. The affinity of the enzyme for isocitrate and NADP-+ was also reduced markedly above 60 degrees. The activation energy calculated from Arrhenius plots below and above 60 degrees were 14,500 and 8,000 cal per mole, respectively. These observations suggest a possible conformation change of the enzyme protein at a transition temperature of 60 degrees, and the physiological significance of this in the adaptation of thermophiles to elevated temperatures is discussed.

Bacteria↗
PubMed1975

Inhibtory effect of colicin E2 on transport systems of Escherichia coli in the presence of the rex gene of lambda prophage.

Purified colicin E(2) was found to cause marked inhibition of the permeation rate of o-nitrophenyl-galactoside (ONPG) in several lambda-lysogenic strains of Escherichia coli in the presence of chloramphenicol to prevent prophage induction. The inhibitory effect of colicin E(2) on transport systems was analyzed with cells of E. coli CP78(lambda). The dose of colicin E(2) for the half-maximum inhibition of the ONPG-permeation rate was about 9 molecules of the colicin per bacterium under the aerobic condition, which corresponded to about 1 killing unit per bacterium. Kinetics of the transport of [(14)C]methylthiogalactoside suggested that colicin E(2) began to inhibit the influx rate of beta-galactosides within a few minutes after the colicin addition, and the maximum inhibition reached more than 80%. Extensive leakage of intracellular potassium ion and inhibition of l-proline transport also occurred at the same time. Acid solubilization of cellular deoxyribonucleic acid by the colicin was apparently delayed to the initiation of the transport inhibition. The extents of the inhibition of beta-galactoside transport and leakage of potassium ion by the colicin were extensive in cells lysogenic for wild lambda phage or lambdaind(-), whereas the extents were slight in the nonlysogenic cells or cells carrying lambdarex(-) prophage. It was concluded that the sensitization of membrane transport systems of E. coli cells to colicin E(2) was achieved by the presence of the rex gene product of lambda phage.

Biological Transport↗
PubMed1972

Specific inhibition of cell division by colicin E 2 without degradation of deoxyribonucleic acid in a new colicin sensitivity mutant of Escherichia coli.

A new class of colicin sensitivity mutants of Escherichia coli was isolated whose cell division was specifically inhibited by colicin E(2) without detectable degradation of deoxyribonucleic acid (DNA) at 30 C. The mutant could not form colonies in the presence of colicin E(2) but recovered colony-forming ability by trypsin treatment even after prolonged incubation with the colicin. Addition of colicin E(2) to the exponentially growing mutant inhibited cell division completely but did not induce degradation of DNA into cold acid-soluble materials nor any breakage of DNA strands. Synthesis of DNA in the mutant was not inhibited, and long filamentous cells with multiple nuclear bodies were formed by the action of colicin E(2). Degradation of ribosomal ribonucleic acid and development of prophage lambda, both of which were induced by colicin E(2) in the sensitive cells, did not occur in the mutant. At the elevated temperature, however, the mutant was found to undergo colicin-induced degradation of DNA. No differences in ultraviolet light nor drug sensitivities were observed in the mutant compared to the parent E. coli. The data suggested that colicin E(2) had a specific inhibitory effect on cell division of E. coli that was not a consequence of DNA degradation.

Bacteriological Techniques↗