水稻細胞釋出性蛋白分解酶之誘導及性質分析

Abstract

環境壓力如高鹽、真菌釋出物、吉貝素及改變氮源等處理水稻細胞，對蛋白分解□出之誘導為研究要點。培養基添加2 mM氯化納，能促進細胞之生長，並提高蛋白分解□之合成及釋出。以酪蛋白替代培養基內的無機含氮成分，則在一天後細胞外□活性會急速升高。若培養基除添加酪蛋白外，亦含吉貝素則對□釋出之誘導有加強效果。從核糖核酸之轉漬分析結果顯示，高鹽、真菌釋出物或吉貝素之處理，都能促使□基因之轉錄訊息增高。部分純化之□蛋白，其最適酸鹼值為3.5°在45℃溫度下，□活性仍相當穩定。根據抑制物之檢測結果可以推論，此釋出性蛋白分解□應為硫氫蛋白分解□。

Induction of an extracellular proteinase in rice suspension cultures by salt, fungal elicitor, gibberellic acid or by replacing inorganic nitrogen compounds with casein were investigated. Sodium chloride with concentration of 2 mM stimulated cell growth and increased proteinase excretion. When inorganic nitrogen in the culture medium was replaced with casein, a sharp increase of enzyme activity was observed after one day. Inclusion of both gibberellic acid and casein in the medium showed an additive effect on proteinase induction. The result of RNA blot analysis indicated that proteinase transcripts were enhanced by treatment of gibberellic acid, fungal elicitor or sodium chloride. The partially purified proteinase had an optimum pH of 3.5 at 30℃.The enzyme was stable at 45℃ for at least one hour and inhibited by leupeptin, p-hydroxymercuribenzoic acid or N-ethylmaleimide, but not by phenylmethylsulfonylfluoride. Result of inhibitor test indicates that the excreted proteinase is likely a sulfhydryl proteinase.