Molecular Dissection and Application of an Enzyme-Inhibitor System with Special Reference to a Proteinase That Specifically Decomposes a Hardly Soluble Protein in Food Seeds.

点击翻译按钮获取中文摘要

A recombinant enzyme was produced from gliadain we found as a new cysteine proteinase in wheat seeds. It actually decomposed, though in vitro, gliadin as a major wheat protein and was found to be involved in the proteolysis of the storage protein during germination. Next, we cloned wheat cystatins by screening with oryzacystatin cDNA as a probe. Three cDNA clones encoding cystatins were thus obtained and it was disclosed that all these cystatins belong to the so-called "phytocystatin" family. In the mean time, we produced a recombinant species of gliadain by fusion with glutathione S-transferase (GST). The resultant GST-progliadain elicited a proteolytic activity under a weakly acidic condition, which was strongly inhibited by a commercially available preparation of egg cystatin as well as by oryzacystatin.The activity was also inhibited to a similar extent by two wheat cystatins we obtained recombinantly. All these results suggest the possibility that a system of the proteolysis with wheat cysteine proteinases and its regulation with wheat cystatins can be industrially applied to food processing for flour quality improvement.