关键词: 百合, 兰州百合, 鳞茎, 淀粉磷酸化酶, 纯化, 酶学性质

Abstract: Starch phosphorylase（SP）in bulbs of Lilium davidii var. unicolor was purified and its enzymatic properties were studied. The results indicated that SP activity was improved 14.78 fold by 30%–60% ammonium sulfate fractionation with a final yield of 23% and a subunit of 62.5 kD. The optimal reaction buffer and temperature were citric acid-sodium citrate buffer（pH 5.0）and 30 ℃，respectively. However，SP was sensible to strong acid and it was not suitable for adding phenolic inhibitors（PVP）to the reaction system. The activity was stable under neutral and alkaline conditions，while decreased under pH < 5. In the synthetic direction，Km value for G-1-P was 2.84 mmol · L-1. Furthermore，1 mmol · L-1 Mg2+ and Ca2+ promoted SP activity significantly，K+ and Zn2+ also played a promoting role. Most ions with high concentration（> 10 mmol · L-1）could inhibit SP activity，whereas Na+ enhanced the activity with its
concentration increasing. Besides，the enzyme activity increased by 30% while adding 10 mmol · L-1 ascorbic acid to the reaction system.

Key words: lily, Lilium davidii var. unicolor, bulb, starch phosphorylase, purify, enzymatic properties