Abstract
Leaf senescence is to transfer nutrients from senescent leaves to other tissues. The degradation of proteins is caused by various proteases, and cysteine protease plays an important role in proteolysis during senescence.
In the previous study, we reported a novel protease having Suc-LY-AMC (N-succinyl-Leu-Tyr-aminomethylcoumarin) degradation activity. This activity dramatically increased in acidic conditions during senescence. To determine the function of this protease, we purified and characterized this enzyme from spinach leaves. The purification was carried out using ammonium sulfate fractionation, hydrophobic, anion exchange, and gel-filtration chromatography. During the chromatography of Butyl-Toyopearl, the protease activity was separated into three peaks. These peaks were designated as acid cysteine protease (ACP) 1, ACP 2 and ACP 3 according to their order of elution. In this study, we characterized the properties of ACP 2 and ACP 3, and discussed reaction mechanisms of these proteases.
