Measurement of beta-amylase in malting barley (hordeum vulgareL.). I. Development of a quantitative ELISA for beta-amylase

Abstract

A double antibody, sandwich enzyme-linked immunosorbent assay (ELISA) was developed using polyclonal antibodies specific to beta-amylase to estimate the amount of 'free' (soluble in aqueous saline solution) or 'combined' (extracted with saline solution including reducing agent) beta-amylase protein in barley grain and malt. This ELISA was used to quantify the amount of beta-amylase in barley grain and malt from four varieties grown at nine sites in South Australia in 1993. The antibody used to develop the ELISA reacted differently with beta-amylase depending on whether the source was barley grain or malt, and on the beta-amylase band pattern in isoelectric focussing (IEF) of the barley variety. On the basis of their IEF band patterns barley varieties were divided into two types, designated Bmy1-Sd1 and Bmy1-Sd2. Malting resulted in proteolytic cleavage of the beta-amylase peptide with a reduction in the apparent molecular weight of up to Mr 4000 and the appearance of new malt beta-amylase IEF bands that were more basic. The new malt beta-amylase IEF band patterns still allowed the identification of the Bmy1-Sd1 and Bmy1-Sd2 IEF types despite the change in molecular weight and pI. The data obtained using the beta-amylase ELISA were highly correlated with beta-amylase activity for both the free and combined fractions when the IEF band pattern and its source, barley grain or malt, were taken into account. © 1997 Academic Press Limited.