Polysaccharide hydrolases from leaves of Boscia senegalensis: properties of endo-(1-->3)-beta-D-glucanase.
The leaves of Boscia senegalensis are traditionally used in West Africa in cereal protection against pathogens, pharmacologic applications, and food processing. Activities of alpha-amylase, beta-amylase, exo-(1-->3, 1-->4)-beta-D-glucanase, and endo-(1-->3)-beta-D-glucanase were detected in these leaves. The endo-(1-->3)-beta-D-glucanase (EC 3.2.1.39) was purified 203-fold with 57% yield. The purified enzyme is a nonglycosylated monomeric protein with a molecular mass of 36 kDa and pI > or = 10.3. Its optimal activity occurred at pH 4.5 and 50 degrees C. Kinetic analysis gave Vmax, kcat, and Km values of 659 U/mg, 395 s(-1), and 0.42 mg/mL, respectively, for laminarin as substrate. The use of matrix-assisted laser desorption ionization time-of-flight mass spectrometry and high-performance liquid chromatography revealed that the enzyme hydrolyzes not only soluble but also insoluble (1-->3)-beta-glucan chains in an endo fashion. This property is unusual for endo-acting (1-->3)-beta-D-glucanase from plants. The involvement of the enzyme in plant defense against pathogenic microorganisms such as fungi is discussed.
Dicko
M H
MH
Department of Agrotechnology and Food Sciences, Wageningen University, The Netherlands.
Searle-van Leeuwen
M J
MJ
Traore
A S
AS
Hilhorst
R
R
Beldman
G
G
D000354:Africa, Western; D004795:Enzyme Stability; D004693:Glucan Endo-1,3-beta-D-Glucosidase / Q000302:isolation & purification* / Q000378:metabolism* / Q000494:pharmacology; D005936:Glucans; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis / Q000187:drug effects; D009844:Oligosaccharides / Q000378:metabolism; D018515:Plant Leaves / Q000201:enzymology*; D010945:Plants, Edible / Q000201:enzymology*; D011134:Polysaccharides / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000254:growth & development; D013379:Substrate Specificity
D005936:Glucans; D009844:Oligosaccharides; D011134:Polysaccharides; C008247:laminaran; D004693:Glucan Endo-1,3-beta-D-Glucosidase