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Characterization of two membrane-associated β-glucosidases from maize coleoptiles Feldwisch, Joachim Vente, Andreas Zettl, Rolf Bako, Laszlo Campos Martínez, Narciso Palme, Klaus Glucòsids Biologia molecular vegetal Glucosides Plant molecular biology We isolated membrane vesicles from maize (Zea mays L.) coleoptiles and identified in these vesicles a 58 kDa (pm58) and a 60 kDa (pm60) protein by photoaffinity labelling with 5-azido-[7-3H]indole-3-acetic acid ([3H]N3IAA). Photoaffinity labelling was effectively competed for by auxins as well as by flavonoids. The labelled proteins were solubilized by Triton X-114 from the vesicles and partially purified. Microsequence analysis revealed that pm60 is a beta-glucosidase. This was confirmed by biochemical and immunological analysis. We show that pm60 has a beta-D-glucoside glucohydrolase (EC 3.2.1.21) activity. It uses p-nitro-phenyl beta-D-glucopyranoside (PNPG) as a substrate, with a pH optimum of 5.0. The Km for PNPG is 0.652 mM and the Vmax. 6.24 mumol.min-1.mg-1. The beta-glucosidase activity of pm60 was competitively inhibited by IAA and 1-naphthylacetic acid as well as by gluconolactam and glucose. N-terminal amino-acid-sequence analysis of pm58 revealed similarity to pm60, suggesting that both proteins are encoded by different members of a gene family. 2026-01-22T11:48:01Z 2026-01-22T11:48:01Z 1994-08-15 2026-01-22T11:48:01Z info:eu-repo/semantics/article info:eu-repo/semantics/acceptedVersion Versió postprint del document publicat a: https://doi.org/10.1042/bj3020015 Biochemical Journal, 1994, vol. 302, num.1, p. 15-21 https://doi.org/10.1042/bj3020015 (c) Feldwisch, J. et al., 1994 info:eu-repo/semantics/openAccess Biochemical Society Articles publicats en revistes (Bioquímica i Biomedicina Molecular)