Abstract
Leaf senescence is a program to transfer nutrients from senescent leaves to other tissues. The degradation of proteins is proceeded by various proteases. Especially, cysteine proteases play an important role in proteolysis during senescence.
In the previous study, we reported a novel protease having 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. It is reported here that a full-length cDNA was isolated from senescent leaves of spinach and exhibited high amino acid sequence homologies to senescence-related cysteine proteases, such as RD21 (Arabidopsis thaliana), DCCP (Dianthus caryophyllus), and CPPIC (Zea mays). We discussed gene expression and protein level of senescence-activated cysteine protease in senescent leaves. A possible role and function of this protease are associated with bulk protein degradation and mobilization during leaf senescence.
