On the Nature of the Proteinases Secreted by the Aleurone Layer of Barley Grain

The nature of the proteinases which are secreted by barley aleurone layers in response to gibberellic acid was studied by constructing pH vs. activity curves for the hydrolysis of gelatin by incubation media and aleurone layer extracts. The results indicate that the aleurone layers release several different proteinases. The main component is a labile sulphydryl enzyme with an optimum pH of 3.9. The other enzymes include two sulphydryl proteinases with pH optima between pH 5 and 6.5 and a metal-activated enzyme active at pH 7.0. No differences could be demonstrated between the proteinases released by and retained in the aleurone layers.