ナラワスサビノリにおける硝酸還元酵素の2, 3の性質

概要

論文の詳細を見る
A crude nitrate reductase solution was obtained from Porphyra yezoensis UEDA f. narawaensis MIURA, which had been cultivated on a cultivation ground at Tokyo Bay in Japan; the precipitate formed with ammonium sulfate on a 20 to 40% saturation was used as nitrate reductase material for the present study. Chemically reduced FMN, FAD, and methyl viologen as well as NADH were all effective as electron donors in this enzyme reaction, but NADPH was ineffective. The Km values for nitrate and FMNH2 were 1.2×10-4M and 2×10-4M, respectively. The Km value for NADH was estimated to be nearly 5×10-5M, but some inhibitions were observed at the higher concentrations. Thus, the Km values of the nitrate reductase from Porphyra were essentially the same as those from the higher plants and other algae, but the following facts were characteristic of this reductase. 1) The Porphyra enzyme showed different optimal pH and temperature values depending on electron donors used; they were pH 8.5 and 23-25°C with NADH-dependent activity, and pH 8.0 and 30°C with FMNH2 dependent activity. 2) The optimal temperature at 23-25°C of the NADH-dependent activity was lower than that of enzymes from other plants; this might reflect the fact that Porphyra thalli must be grown during a cold winter season. 3) The nitrate reductase was stimulated by addition of FAD; its Km value was estimated to be 1×10-7M.
公益社団法人日本水産学会の論文