This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Miller, B. L. Articles by Huffaker, R. C. Search for Related Content PubMed PubMed Citation Articles by Miller, B. L. Articles by Huffaker, R. C. Agricola Articles by Miller, B. L. Articles by Huffaker, R. C.

Articles

Partial Purification and Characterization of Endoproteinases from Senescing Barley Leaves ¹

Plant Growth Laboratory and Department of Agronomy and Range Science, University of California at Davis, Davis, California 95616

Two major endoproteinases were purified from senescing primary barley leaves. The major enzyme (EP₁) appeared to be a thiol proteinase and accounted for about 85% of the total proteolytic activity measured in vitro. This proteinase was purified 5,800-fold and had a molecular weight of 28,300. It was highly unstable in the absence of dithiothreitol or at a pH greater than 7.5. Leupeptin, at a concentration of 10 micromolar, inhibited this enzyme 100%. A second proteinase (EP₂) was purified approximately 50-fold and had a molecular weight of 67,000. It was inhibited 20% by 1 millimolar dithiothreitol and 50% by 1 millimolar phenylmethyl sulfonylfluoride. EP₂ contributed about 15% of the total proteolytic activity measured in vitro. Both proteinases hydrolyzed a variety of artificial and protein substrates, and both had pH optima of 5.5 to 5.7 when either azocasein or [¹⁴C]ribulose-1,5-bisphosphate carboxylase ([¹⁴C]RuBPCase) was the substrate. The thiol endoproteinase hydrolyzed azocasein linearly but hydrolyzed [¹⁴C]RuBPCase biphasically. A third endoproteinase (EP₃), not detected by standard proteolytic assays, was observed when [¹⁴C]RuBPCase was the substrate.

This article has been cited by other articles:

				G. R. Pichard, B. R. Tesser, C. Vives, C. Solari, A. Hott, and R. E. Larrain Proteolysis and Characterization of Peptidases in Forage Plants Agron. J., October 3, 2006; 98(6): 1392 - 1399. [Abstract] [Full Text] [PDF]

				R. Nakano, H. Ishida, A. Makino, and T. Mae In vivo Fragmentation of the Large Subunit of Ribulose-1,5-Bisphosphate Carboxylase by Reactive Oxygen Species in an Intact Leaf of Cucumber under Chilling-light Conditions Plant Cell Physiol., February 1, 2006; 47(2): 270 - 276. [Abstract] [Full Text] [PDF]

				A. Chiba, H. Ishida, N. K. Nishizawa, A. Makino, and T. Mae Exclusion of Ribulose-1,5-bisphosphate Carboxylase/oxygenase from Chloroplasts by Specific Bodies in Naturally Senescing Leaves of Wheat Plant Cell Physiol., September 15, 2003; 44(9): 914 - 921. [Abstract] [Full Text] [PDF]