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Biomedical subjects

K Osada

Publications and source records attributed to K Osada.

At least 109 records · Page 6Linked to original sources
PubMed1984

L-tryptophan 2,3-dioxygenase of a moderate thermophile, Bacillus brevis. Purification, properties and a substrate-mediated stabilization of the quaternary structure.

L-Tryptophan 2,3-dioxygenase (L-tryptophan: oxygen 2,3-oxidoreductase ( decycling ), EC 1.13.11.11) from Bacillus brevis, a moderately thermophilic bacteria, was purified to apparent homogeneity. The enzyme had a molecular weight of 110 000 and consisted of four subunits of equal molecular size. The enzyme exhibited the typical absorption spectra of a protohemoprotein . The amino acid composition and catalytic properties of the thermophilic enzyme were almost similar to those of its mesophilic counterpart from Pseudomonas acidovorans. However, the stabilities of the enzyme differed markedly between the two. The thermophilic enzyme was more resistant to heat and several chemical denaturants. The addition of L-tryptophan protected the enzyme from heat- and SDS- denaturations , and the tryptophan-mediated stabilization was more evident for the thermophilic enzyme. The effect of L-tryptophan on the stabilization of the thermophilic enzyme was more effective in preventing the dissociation of the tetrameric form of the enzyme (i.e. stabilizing it) in the case of the native, as compared to the mesophilic enzyme.

Amino Acids↗
PubMedDate not supplied

Enhancement of interferon-beta production with sphingomyelin from fermented milk.

A fermented milk, Kefir, contains an active substance which enhances IFN-beta secretion of a human osteosarcoma line MG-63 treated with a chemical inducer, poly I: poly C. The active substance in the fermented milk was identified to be sphingomyelin (SpM) by a combined use of a fast atom bombardment mass spectrometry (FAB-MS) and a fast atom bombardment tandem mass spectrometry (FAB-MS/MS). SpM from fermented milk (F-SpM) was a mixture of four molecular species of SpMs having C21-, C22-, C23- and C24-fatty acids. F-SpM enhanced the IFN secretion 14 times, SpMs from other sources also enhanced moderately (2-3 times). Sphingosine and lysosphingomyelin also enhanced the activity but ceramide and cerebroside did not.

Animals↗