Tadashi Kurokawa

Formation of polyprenyl phosphates by a cell-free enzyme of Micrococcus lysodeikticus.

Abstract A cell-free enzyme of Micrococcus lysodeikticus catalyzed the formation of polyprenyl phosphates ranging in carbon chain from C-20 to C-55 with a predominance of C-40. Homogenates of rabbit liver (or kidney) and yeast catalyzed effectively the hydrolysis of these long chain prenyl phosphates but did not act on the pyrophosphate esters.

Generation of free radicals and initiation of radical reactions in nitrones — Fe2+ - phosphate buffer systems

Abstract Stability of spin trapping reagents, phenyl-tert-butylnitrone (PBN) and 5,5-dimethyl-pyrroline-N-oxide (DMPO), in Fe2+-phosphate buffer (pH 7.8 and 7.0) was examined. Both nitrones generate the spin adducts without substrate. It was supposed that PBN and DMPO produce the benzoyl and hydroxyl spin adducts, respectively, by the decomposition of themselves in the system. The presence of alcohols causes the initiation of radical reaction and leads to strong ESR signals due to hydroxyalkyl spin adducts.

A new prenyltransferase from Micrococcus lysodeikticus.

Abstract A new prenyltransferase which catalyzes the synthesis of geranyl pyrophosphate as the only product from dimethylallyl pyrophosphate and isopentenyl pyrophosphate has been separated from other known prenyltransferases from Micrococcus lysodeikticus . This enzyme fraction is also capable of synthesizing all- trans geranylgeranyl pyrophosphate from farnesyl pyrophosphate and isopentenyl pyrophosphate though it lacks ability to synthesize farnesyl pyrophosphate.

Inhibitory effect of cytokinins on PHA-induced human lymphocyte stimulation.

The inhibitory effect of various purine derivatives on PHA-induced human lymphocyte blast formation was studied. Two nucleoside cytokinins, N6-benzyladenosine and N6-isopentenyladenosine, inhibited blast formation at concentrations as low as 10−6 M. However, the other cytokinins, which lacked the ribosyl residue at N9 position, had to be at the higher molar concentration of 10−4 before they could induce the same inhibitory effect.

Biochemical examination on the increased superoxide dismutase-like plasma substance observed in a state of acute gastric mucosal lesions

When experimental acute gastric mucosal lesions were produced in guinea pig by water-immersion and restraint stress, superoxide dismutase (SOD)-like substance in the plasma increased. On analysis by gel filtration, it was shown that the molecular weight of the increased SOD-like plasma substance was about 130,000, and even after treatment with trypsin, 84% of this substance remained. Since the molecular weight of intracellular SOD is about 40,000, it seems that this substance is similar to extracellular SOD, located on the endothelial cell-surface, as previously reported by Marklund et al. Our results suggest that in the presence of acute gastric mucosal lesions, SOD-like plasma substance is not identical to intracellular SOD, which derived from cell destruction by stress or free radical-induced microvascular damage or by hemolysis. Furthermore, this substance may itself work as a scavenger of free radicals generated under conditions, such as these described in the present experiment.