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Some thaumatin‐like proteins hydrolyse polymeric β‐1,3‐glucans
Author(s) -
Grenier Jean,
Potvin Claude,
Trudel Jean,
Asselin Alain
Publication year - 1999
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1046/j.1365-313x.1999.00551.x
Subject(s) - thaumatin , laminarin , biochemistry , enzyme , glucanase , chemistry , hydrolysis , xyloglucan , hydrolase , amino acid , gene
Summary Thaumatin and 12 purified thaumatin‐like (TL) proteins were surveyed for their capacity to hydrolyse β‐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 β‐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‐β‐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 β‐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‐β‐1,3‐glucanase activity on polymeric β‐1,3‐glucans.