A single-chained ribonuclease was isolated from the aqueous extract of sanchi ginseng (Panax pseudoginseng) flowers. It exhibited a molecular mass of 23 kDa, an N-terminal sequence with some similarity to other enzymes involved in RNA metabolism but different from known ribonucleases, and considerably higher activity toward poly U than poly C and only slight activity toward poly A and poly G. The purification protocol entailed ion exchange chromatography on diethylaminoethyl (DEAF)-cellulose, affinity chromatography on Affi-gel blue gel, ion exchange chromatography on carboxymethyl (CM)-cellulose, and gel filtration on Superdex 75. The ribonuclease was unadsorbed on DEAF-cellulose and adsorbed on Affi-gel blue gel and CM-cellulose. Maximal activity of the ribonuclease was attained at pH 7. On either side of this pH the enzyme activity underwent a drastic decline. The enzyme activity was at its highest at 50 degrees C and dropped to about 20% of the maximal activity when the temperature was decreased to 20 degrees C or elevated to 80 degrees C. The characteristics of sanchi ginseng flower ribonuclease were different from those of the ribonucleases previously purified from sanchi ginseng and Chinese ginseng roots including ribonuclease from Chinese ginseng flowers which are morphologically very similar to sanchi ginseng flowers. (c) 2006 Elsevier Inc. All rights reserved.