Barley and Malt Proteins and Proteinases: II. The Purification and Characterisation of Five Malt Endoproteases, Using the Highly Degradable Barley Protein Fraction (HDBPF) Substrate

Abdalla M. Osman ^1
1Leslie Research Centre, Farming Systems Institute, Queensland Department of Primary Industries, Agency for Food and Fibre Sciences, P O Box 2282, Toowoomba, QLD 4350, Australia. Corresponding author. E-mail: Abdalla.Osman@dpi.qld.gov.au

J. Inst. Brew. 109(2), 142-149, 2003  |   VIEW ARTICLE

ABSTRACT
Five barley-malt endoproteases have been purified using the highly degradable barley protein fraction (HDBPF) as the substrate for activity detection and measurement. The five purified endoproteases were identified as the most active and, hence, we believe the most important proteolytic enzymes during barley germination and malting. This was demonstrated by showing that the component of HDBPF, degraded in test tubes during the reaction to determine their activity, cannot be recovered from malt by extraction, indicating that this component has been degraded during germination and malting. These endoproteases differ in their specificities, pH and temperature optima, thermostability and ionic-cationic behaviour. The gel filtration chromatographic-profiles of the peptide products of these enzymes versus parallel profiles of beer peptides exhibit very close similarities.

Key words:
Barley protein substrates, characterisation, malt endoproteases, proteinases, purification.

Publication no. G-2003-1616-110  ^©2003 The Institute & Guild of Brewing