米麹の褐変に関する研究 : (第6報)米麹チロシナーゼと麹菌体チロシナーゼとの性質の比較

概要

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The characteristics of the browning activity of extracts from rice-koji prepared by using Aspergillus oryzae, strain RIB 128(ATCC 22788) , which always makes rice-koji brown, and the activity from the mycelia of the same strain obtained by submerged culture were compared with that of commercial tyrosinase from the mushroom.1. It was found that all these enzyme preparations catalyzed the conversion from _L-tyrosine to _L-dopa and, further, to melanin.2. The optimum pH and temperature for thr enzyme extracted from rice-koji were at pH 6 and 40 ℃. Those for the enzyme extracted from the mycelia were at pH 5 and 30-40 ℃.3. These enzyme preparations were inactivated by heat treatment at 70℃ for 15 min.4. All of these preparations were inhibited by copper chelating agents, such as sodium diethyldithiocarbamate, potassium metabisulfite, sodium cyanide, thiourea, and sodium azide at concentrations of 10^<-3> M.Thus, the enzyme concerned in the browning of rice-koji produced by the culture of A. oryzae was regarded as tyrosinase.
社団法人日本生物工学会の論文