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Biomedical subjects

K Takai

Publications and source records attributed to K Takai.

At least 289 records · Page 16Linked to original sources
PubMed1977

Crystalline hemoprotein from Pseudomonas that catalyzes oxidation of side chain of tryptophan and other indole derivatives.

A new enzyme which catalyzes the oxidation of the side chain of tryptophan and other indole derivatives, has been purified to apparent homogeneity from Pseudomonas and crystallized. The overall purification was about 25-fold with a yield of 4.5%. The purified enzyme was apparently homogeneous as judged by polyacrylamide gel electrophoresis. The molecular weight estimated by gel filtration was approximately 280,000 and sedimentation coefficient (S20,w) was 11 by sucrose density gradient ultracentrifugation. The absorption spectra indicated that the enzyme was a hemoprotein. The purified enzyme was shown to catalyze the reaction in which 1 mol each of NH3 and CO2 was formed at the expense of 1 mol each of L-tryptophan and molecular oxygen. Neither peroxidase nor catalase activity was detected in the purified enzyme and no formation of H2O2 was observed during the enzyme reaction. The product(s) of the reaction was unstable but was converted to and was identified as its stable quinoxaline derivative, 2-(3-indolyl)quinoxaline, in the presence of o-phenylenediamine. These results indicate that the product of the reaction was 3-indolylglycoaldehyde or 3-indolylglyoxal. A variety of other indole derivatives such as D-tryptophan, 5-hydroxyl-L-tryptophan, tryptamine, serotonin, melatonin, N-acetyl-L-tryptophan, N-acetyl-L-tryptophanamide, 3-indoleacetamide, 3-indolelactic acid, 3-indolepropionic acid, 3-indoleethanol, and skatole were also substrates.

Chromatography, Thin Layer↗
PubMed1975

Oligonucleotide sequences of pancreatic and T1 ribonuclease digests of 5S ribosomal RNA from mouse cells.

Oligonucleotides produced by complete pancreatic and T1 RNase digestion of 5S ribosomal RNA from a mouse hepatoma, MH 134, have been separated with two-dimensional electrophoresis and their nucleotide sequences determined. Except for the presence of a 5'-terminal diphosphate, these nucleotide sequences were identical with those of KB cells, confirming the identity of the primary structure of 5S RNA between these animals. Both oligonucleotide patterns produced with these enzymes from 5S RNA of the liver were also identical with those of the hepatoma. All these agree with the strong conservation of 5S RNA genes in animal species. However, when 5S ribosomal RNA was extracted from ribosomes which were prepared from microsomal pellet, pancreatic RNase digest contained two trinucleotides (A-G-Cp and G-A-Cp) that were not found in 5S RNA prepared with a one-step procedure. It was concluded that different isolation procedure might indeed cause artifactual fragments on enzymatic digestion due to internal nicks produced during isolation. The significance of 5'-terminal diphosphate in relation to the biosynthesis of 5S ribosomal RNA is also discussed.

Animals↗
PubMed1974

Adenylate cyclase from Brevibacterium liquefaciens. III. In situ regulation of adenylate cyclase by pyruvate.

In the presence of DL-alanine intracellular cyclic AMP in nonproliferating cells of Brevibacterium liquefaciens increased rapidly to the maximum level of approximately 180 muM, and extracellular cyclic AMP increased to 100 muM within 4 hr at 25 degrees . Adenylate cyclase (EC 4.6.1.1) induction was not observed during this incubation. The concentration of pyruvate in the total culture increased concomitantly with that of cyclic AMP and reached approximately 20 mM after 4 hr of incubation. Since the activity of cyclic nucleotide phosphodiesterase is extremely low in this bacterium, the accumulation of cyclic AMP with DL-alanine appeared to be due to the activation of adenylate cyclase by pyruvate. D-alanine was more effective than L-alanine in producing pyruvate, and a high activity of D-alanine oxidation was detected in the cell lysate of B. liquefaciens.Thus, adenylate cyclase in this bacterium appeared to be regulated in vivo by pyruvate which was formed, in this case, predominantly from D-alanine through the action of D-aminoacid oxidase (EC 1.4.3.3). Pyruvate, added extracellularly, also caused a rapid accumulation of intracellular cyclic AMP. Glucose did not change the level of cyclic AMP significantly. It also did not affect the intracellular accumulation of cyclic AMP with DL-alanine.

Adenylyl Cyclases↗