Some thaumatin-like proteins hydrolyse polymeric beta-1,3-glucans

• Published in: The Plant journal : for cell and molecular biology 1999-08, Vol.19 (4), p.473-480
• Main Authors: Grenier, J, Potvin, C, Trudel, J, Asselin, A
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Amino Acid Sequence; amino acid sequences; beta-glucanase; beta-Glucans; Biological and medical sciences; Cell Wall - metabolism; Chromatography, Thin Layer; Economic plant physiology; enzyme activity; Enzymes; fruits; Fundamental and applied biological sciences. Psychology; Glucan Endo-1,3-beta-D-Glucosidase - metabolism; Glucans - metabolism; Hordeum vulgare; Hydrolysis; Kinetics; leaves; Metabolism; Molecular Sequence Data; Nicotiana tabacum; Nutrition. Photosynthesis. Respiration. Metabolism; O-glycoside hydrolases; Pisum sativum; plant pathogenic fungi; Plant physiology and development; plant proteins; Plant Proteins - metabolism; Plant Structures - enzymology; Plant Structures - metabolism; Polymers; Prunus avium; Saccharomyces cerevisiae; Sequence Analysis, Protein; Sequence Homology, Amino Acid; Solanum lycopersicum var. lycopersicum; Solubility; Space life sciences; Spores, Fungal - metabolism; stigma; Substrate Specificity; substrates; Sweetening Agents; Yeasts - cytology; Zea mays
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1046/j.1365-313X.1999.00551.x

Thaumatin and 12 purified thaumatin-like (TL) proteins were surveyed for their capacity to hydrolyse beta-1,3-glucans by using an in-gel glucanase assay. Six TL proteins identified by N-terminal amino acid microsequencing were found to be active on carboxymethyl(CM)-pachyman: a barley leaf stress-related permatin, two tomato fruit osmotins, a cherry fruit and two tobacco stigma proteins. TL enzymes ranged in specific activity from 0.07 to 89 nkat mg(-1) with CM-pachyman as substrate. Hydrolytic activities were not restricted to TL proteins strongly binding to water-insoluble beta-1,3-glucans since the two osmotins were active without tight binding to pachyman. Some TL proteins hydrolysed crude fungal walls and one barley TL enzyme even lysed fungal spores. No activity was observed on laminarin in the in-gel hydrolase assay. Thin-layer chromatography revealed that the six enzymes acted as endo-beta-1,3-glucanases leading to the formation of various oligoglucosides. Thus far, the TL enzymes (EC 3.2.1.x) appeared different from the well-known beta-1,3-glucanases (EC 3.2.1.39). No activity was found with thaumatin, zeamatin, tobacco leaf PR-R protein and four stress-related TL proteins from barley and pea. This is the first demonstration that diverse TL proteins are enzymatically active. The functions of some TL proteins must be reassessed because they display endo-beta-1,3-glucanase activity on polymeric beta-1,3-glucans.