Keiji Sakamoto

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Lactone compounds are widely distributed in nature and play important roles in organisms. These compounds are synthesized and metabolized enzymatically in vivo; however, detailed investigation of these enzymes lags behind that of other common enzymes. In this paper, recent work on the enzymes involved in the metabolism of lactone compounds will be reviewed.(More)
To examine the effects of frequent fires on species composition of the boreal forest in northern Mongolia, we investigated regeneration patterns, including reproductive pathways, post-fire seed sources, and site preferences, of four common tree species (Betula platyphylla, Larix sibirica, Picea obovata, and Pinus sibirica). Regeneration patterns differed(More)
A novel esterase catalyzing regioselective hydrolysis was purified from the membrane fraction of Microbacterium sp. 7-1W, and characterized. The enzyme was solubilized with Brij 58 and purified 13.8-fold to apparent homogeneity with 2.58% overall recovery. The relative molecular mass of the native enzyme as estimated by gel filtration was more than 600,000(More)
In arid and semiarid regions, variations in “islands of fertility” accompanied by discontinuous vegetation is frequently observed. However, the effects of vegetation patches on soil, including the influence of canopy size, are not fully understood, particularly under conditions of severe grazing. We examined the effects of patches of mound-forming shrub,(More)
We developed an enzymatic resolution system for DL-pantoyl lactone that uses immobilized mycelia of Fusarium oxysporum, which produce a lactone-hydrolyzing enzyme (lactonase). The lactonase catalyzes the stereospecific hydrolysis of D-pantoyl lactone. One hundred eighty repeated batch reactions (total reaction time, 3780 h) were made with mycelia entrapped(More)
A mouse model for the study of postexposure prophylaxis of rabies was established. Mice injected intramuscularly with a street strain of rabies virus were significantly protected from death by five daily 0.2-ml doses of inactivated rabies vaccine of chick embryo cell culture origin initiated immediately or 3 hr after infection. In these mice, a large amount(More)
The lactonase gene of Fusarium oxysporum was expressed in Aspergillus oryzae for optical resolution of dl-pantoyl lactone. When the chromosomal gene encoding the full-length form of the lactonase, which has its own NH2-terminal signal peptide, was introduced in the host cells, the resulting transformant produced an enzyme of 46,600 Da, which corresponded to(More)
NADP+-dependent aminoalcohol dehydrogenase (AADH) of Rhodococcus erythropolis MAK154 catalyzes the reduction of (S)-1-phenyl-1-keto-2-methylaminopropane ((S)-MAK) to d-pseudoephedrine, which is used as a pharmaceutical. AADH is suggested to participate in aminoalcohol or aminoketone metabolism in this organism because it is induced by the addition of(More)
The aminoalcohol dehydrogenase (AADH) of Rhodococcus erythropolis MAK154, which can be used as a catalyst for the stereoselective reduction of (S)-1-phenyl-1-keto-2-methylaminopropane to d-pseudoephedrine (dPE), is inhibited by the accumulation of dPE in the reaction mixture, limiting the yield of dPE. To improve this weak point of the enzyme, random(More)
Athymic nude mice injected intramuscularly with a street stain of rabies virus were not protected against rabies by postexposure administration of beta-propiolactone-inactivated rabies vaccine. In contrast, their normal littermates were completely protected from death by the same vaccination regimens. Nude mice did not produce IgG antibody as a result of(More)