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Plant Physiology 80:692-697 (1986)
© 1986 American Society of Plant Biologists

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Articles

Hormonal Regulation of the Development of Protease and Carboxypeptidase Activities in Barley Aleurone Layers 1

Rachel W. Hammerton2 and Tuan-Hua David Ho

Department of Plant Biology, University of Illinois, Urbana, Illinois 61801-4777, Department of Biology, Washington University, St. Louis, MO 63130

Carboxypeptidase and protease activities of hormone-treated barley (Hordeum vulgare cv Himalaya) aleurone layers were investigated using the substrates N-carbobenzoxy-Ala-Phe and hemoglobin. A differential effect of gibberellic acid (GA3) on these activities was observed. The carboxypeptidase activity develops in the aleurone layers during imbibition without the addition of hormone, while the release of this enzyme to the incubation medium is enhanced by GA3. In contrast, GA3 is required for both the production of protease activity in the aleurone layer and its secretion. The time course for development of protease activity in response to GA3 is similar to that observed for {alpha}-amylase. Treating aleurone layers with both GA3 and abscisic acid prevents all the GA3 effects described above. Carboxypeptidase activity is maximal between pH 5 and 6, and is inhibited by diisopropylfluorophosphate and p-hydroxymercuribenzoate. We have observed three protease activities against hemoglobin which differ in charge but are all 37 kilodaltons in size on sodium dodecyl sulfate polyacrylamide gels. The activity of the proteases can be inhibited by sulfhydryl protease inhibitors, such as bromate and leupeptin, yet is enhanced by 2-fold with 2-mercaptoethanol. In addition, these enzymes appear to be active against the wheat and barley storage proteins, gliadin and hordein, respectively. On the basis of these characteristics and the time course of GA3 response, it is concluded that the proteases represent the GA3-induced, de novo synthesized proteases that are mainly responsible for the degradation of endosperm storage proteins.

2 Present address: Department of Horticulture, University of Illinois, 1103 W. Dorner Dr., Urbana, IL 61801.

1 Supported by United States Department of Agriculture competitive grant AG 82-CRCR-1-1012 and by National Science Foundation grant PCM 80-21632.




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A. M. Shirley and C. Chapple
Biochemical Characterization of Sinapoylglucose:Choline Sinapoyltransferase, a Serine Carboxypeptidase-like Protein That Functions as an Acyltransferase in Plant Secondary Metabolism
J. Biol. Chem., May 23, 2003; 278(22): 19870 - 19877.
[Abstract] [Full Text] [PDF]


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Copyright © 1986 by the American Society of Plant Biologists