Changes in the cationic isoenzymes of peroxidase during the malting of barley .2. The effect of gibberellic and abscisic acids

During germination, alpha-amylase activity in barley (variety: Chariot) increased 29-fold, while peroxidase activity increased 4.2-fold. Increasing concentrations of GA(3) increased the rate of development of alpha-amylase activity while the rate of increase of peroxidase activity remained unchanged, but there was an overall increase in the amount of peroxidase synthesized. ABA caused a concentration-dependent suppression of activity and a decrease in the rate of expression of both enzymes. Three different types of response of individual peroxidase isoenzymes occurred during germination. Six isoenzymes increased in activity during malting, four decreased in activity and nine showed a rise at the beginning of germination followed by a significant fall. The majority of the isoenzymes were positively GA(3)-sensitive, ie increased in activity or were synthesized earlier in the presence of GA(3), and negatively ABA-sensitive. Only four isoenzymes were negatively GA(3)-sensitive, and only three were positively ABA-sensitive. Detailed data for the synthesis during germination of the six major peroxidase isoenzymes that survive into the finished malt is presented.