Barley and Malt Proteins and Proteinases: Ⅰ. Highly Degradable Barley Protein Fraction (HDBPF), a Suitable Substrate for Malt Endoprotease Assay

摘要

Barley grain proteins were extracted and fractionated, based on their solubility, to investigate their proteolytic digestibility and suitability to be used as a substrate for the assay of malt protein-ases. The fraction extracted with alkaline buffer (Tris-HCl or Tris-glycine pH 8.8-9.5), at the end of the sequence, exhibited remarkably high degradability by malt proteases compared to other fractions or any known protein substrate. Gel filtration chromatographic analysis of this fraction revealed that it is composed of three different molecular weight components. Further investigation, after proteolytic treatment, demonstrated that the third and the low molecular weight component is the highly degradable protein(s) (HDP). We designated the whole fraction, the mixture of the three components, as the highly degradable barley protein fraction (HDBPF) and used it (and recommend it) as the substrate for the assay of malt endoproteases activity.