Daurichromenic acid (DCA) synthase catalyzes the oxidative cyclization of grifolic acid to produce DCA, an anti-HIV meroterpenoid isolated from We identified a novel cDNA encoding DCA synthase by transcriptome-based screening from young leaves of The gene coded for a 533-amino acid polypeptide with moderate homologies to flavin adenine dinucleotide oxidases from other plants. The primary structure contained an amino-terminal signal peptide and conserved amino acid residues to form bicovalent linkage to the flavin adenine dinucleotide isoalloxazine ring at histidine-112 and cysteine-175. In addition, the recombinant DCA synthase, purified from the culture supernatant of transgenic , exhibited structural and functional properties as a flavoprotein. The reaction mechanism of DCA synthase characterized herein partly shares a similarity with those of cannabinoid synthases from, whereas DCA synthase catalyzes a novel cyclization reaction of the farnesyl moiety of a meroterpenoid natural product of plant origin. Moreover, in this study, we present evidence that DCA is biosynthesized and accumulated specifically in the glandular scales, on the surface of plants, based on various analytical studies at the chemical, biochemical, and molecular levels. The extracellular localization of DCA also was confirmed by a confocal microscopic analysis of its autofluorescence. These data highlight the unique feature of DCA: the final step of biosynthesis is completed in apoplastic space, and it is highly accumulated outside the scale cells.

SynopsisThe melting rate of iron oxide pellets into iron melt and the reduction rate of pellets by carbon in iron melt were obtained by measuring the evolution rate of CO gas. The pellets were made from iron oxide powder by pressing and sintering and were not crushed into pieces when added onto the iron melt. The effects of the iron oxide phase, the oxide additives in pellets, and the temperature and the carbon content of iron melts on the melting and the reduction rates were investigated. The following results were obtained:(1) It has been found that the heat transfer was not the rate-determining step for the two rates. It is considered that the carbon diffusion in a boundary layer on the iron melt surface could be the rate-determining step.(2) The total reduction rate was constant for reduction degrees from about 20% to about 70%, where solid iron oxides were reduced by carbon dissolved in iron melt.(3) The apparent activation energy of the melting of pellets into the carbon saturated iron melt was 35 for Fe203; 18 and 41 for Fe304 above and below 1470°C, respectively; 44 and 79 kcal/mol for FeO above and below 1470°C, respectively.(4) The melting rate of Fe203, Fe304 and FeO pellets into the iron melt at 1570°C was proportional to C057, C045 and G042 respectively, where C denotes the weight percentage of carbon in an iron melt. The minimum amount of CO gas evolved was obtained at about 2%C.

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The fundamental aspect q! the development of the NRIM multi-stage trough type continuous steelmaking process and the results of its recent operations are presented in this jJaper. Though the scale of the plant used was small (7.8 tlhr in hot metal flow rate), a suitable sejJaration of the steelmaking reactions to each stage of the continuous steelmaking furna ce and the know-how qf its ojJeration were satiifactorily obtained. As the result of the separation, that is, silicon and phosphorus were mostly removed in the first stage so that the final carbon level was controlled mainly in the second stage, the p roduct with phosphorus as low as 0.005% (dephosjJhoriz ation rate 96%) was obtained with comparable amount of lime to that of the conventional batch type steelmaking processes. The industrializ ation of this process is confirmed to be feasible.