Avenacosidase from oat: purification, sequence analysis and biochemical characterization of a new member of the BGA family of beta-glucosidases.

Abstract

A protein consisting of 60 kDa subunits (As-P60) was isolated from etiolated oat seedlings (Avena sativa L.) and characterized as avenacosidase, a beta-glucosidase that belongs to a preformed defence system of oat against fungal infection. The enzyme is highly aggregated; it consists of 300-350 kDa aggregates and multimers thereof. Dissociation by freezing/thawing leads to complete loss of enzyme activity. The specificity of the enzyme was investigated with para-nitrophenyl derivatives which serve as substrates, in decreasing order beta-fucoside, beta-glucoside, beta-galactoside, beta-xyloside. The corresponding orthonitrophenyl glycosides are less well accepted. No hydrolysis was found with alpha-glycosides and beta-thioglucoside. An anti-As-P60 antiserum was prepared and used for isolation of a cDNA clone coding for As-P60. A presequence of 55 amino acid residues was deduced from comparison of the cDNA sequence with the N-terminal sequence determined by Edman degradation of the mature protein. The presequence has the characteristics of a stroma-directing signal peptide; localization of As-P60 in plastids of oat seedlings was confirmed by western blotting. The amino acid sequence revealed significant homology (> 39% sequence identity) to beta-glucosidases that are constituents of a defence mechanism in dicotyledonous plants. 34% sequence identity was even found with mammalian and bacterial beta-glucosidases of the BGA family. Avenacosidase extends the occurrence of this family of beta-glucosidases to monocotyledonous plants.

• Authors: S Gus-Mayer, H Brunner, H A Schneider-Poetsch, W Rüdiger
• Journal: Plant molecular biology (Plant Mol Biol) Vol. 26 Issue 3 Pg. 909-21 (Nov 1994) ISSN: 0167-4412 [Print] Netherlands
• PMID: 8000004 (Publication Type: Comparative Study, Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Glycosides
• Protein Sorting Signals
• Recombinant Fusion Proteins
• avenacosidase
• beta-Glucosidase

Topics

• Amino Acid Sequence
• Avena (enzymology, genetics)
• Base Sequence
• Blotting, Northern
• Blotting, Western
• Cell Compartmentation
• Genes, Plant (genetics)
• Glycosides (metabolism)
• Molecular Sequence Data
• Multigene Family
• Plastids (enzymology)
• Protein Sorting Signals (genetics)
• Recombinant Fusion Proteins (biosynthesis)
• Sequence Analysis
• Sequence Homology, Amino Acid
• Substrate Specificity
• beta-Glucosidase (biosynthesis, classification, genetics, immunology, metabolism)