title: Aspartic proteinase from barley grains is related to mammalian lysosomal cathepsin D.
abstract: 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 48k Da 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 48k Da form. Amino-acid sequence alignment and inhibition studies showed that the barley aspartic proteinase resembles mammalian lysosomal cathepsin D (EC 3.4.23.5).
authors.affiliation: Department of Biology, University of Jyväskylä, Seminaarinkatu 15, SF-40100, Jyväskylä.
authors.forename: P
authors.initials: P
authors.lastname: Sarkkinen
authors.forename: N
authors.initials: N
authors.lastname: Kalkkinen
authors.forename: C
authors.initials: C
authors.lastname: Tilgmann
authors.forename: J
authors.initials: J
authors.lastname: Siuro
authors.forename: J
authors.initials: J
authors.lastname: Kervinen
authors.forename: L
authors.initials: L
authors.lastname: Mikola