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Aspartic proteinase from barley grains is related to mammalian lysosomal cathepsin D
Paula Sarkkinen, Nisse Kalkkinen, Carola Tilgmann, Jari Siuro, Jukka Kervinen and Leena Mikola
Vol. 186, No. 3 (1992), pp. 317-323
Published by: Springer
Stable URL: http://www.jstor.org/stable/23381457
Page Count: 7
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Resting barley (Hordeum vulgare L.) grains contain acid-proteinase activity. The corresponding enzyme was purified from grain extracts by affinity chromatography on a pepstatin-Sepharose column. The pH optimum of the affinity-purified enzyme was between 3.5 and 3.9 as measured by hemoglobin hydrolysis and the enzymatic activity was completely inhibited by pepstatin — a specific inhibitor of aspartic proteinases (EC 3.4.23). Further purification on a Mono S column followed by activity measurements and sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that the affinity-purified enzyme preparation contained two active heterodimeric aspartic proteinases: a larger 48-kDa enzyme, consisting of 32-kDa and 16-kDa subunits and a smaller one of 40 kDa, consisting of 29-kDa and 11-kDa subunits. Separation and partial amino acid sequence analysis of each subunit indicate that the 40-kDa enzyme is formed by proteolytic processing of the 48-kDa form. Amino-acid sequence alignment and inhibition studies showed that the barley aspartic proteinase resembles mammalian lysosomal cathepsin D (EC 126.96.36.199).
Planta © 1992 Springer