Taxonomic group: bacteria, fungi / Proteobacteria, Basidiomycota
(Phylum: Proteobacteria, Basidiomycota)
NCBI PubMed ID: 8424790Publication DOI: 10.1042/bj2890453Journal NLM ID: 2984726RPublisher: London, UK : Published by Portland Press on behalf of the Biochemical Society
Institutions: Department of Biochemistry, La Trobe University, Bundoora, Victoria, Australia
Three (1→3)-β-D-glucan glucanohydrolase (EC 3.2.1.39) isoenzymes GI, GII and GIII were purified from young leaves of barley (Hordeum vulgare) using (NH4)2SO4 fractional precipitation, ion-exchange chromatography, chromatofocusing and gel-filtration chromatography. The three (1→3)-β-D-glucanases are monomeric proteins of apparent M(r)32,000 with pI values in the range 8.8-10.3. N-terminal amino-acid-sequence analyses confirmed that the three isoenzymes represent the products of separate genes. Isoenzymes GI and GII are less stable at elevated temperatures and are active over a narrower pH range than is isoenzyme GIII, which is a glycoprotein containing 20-30 mol of hexose equivalents/mol of enzyme. The preferred substrate for the enzymes is laminarin from the brown alga Laminaria digitata, an essentially linear (1→3)-β-D-glucan with a low degree of glucosyl substitution at 0-6 and a degree of polymerization of approx. 25. The three enzymes are classified as endohydrolases, because they yield (1→3)-β-D-oligoglucosides with degrees of polymerization of 3-8 in the initial stages of hydrolysis of laminarin. Kinetic analyses indicate apparent Km values in the range 172-208 microM, kcat. constants of 36-155 s-1 and pH optima of 4.8. Substrate specificity studies show that the three isoenzymes hydrolyse substituted (1→3)-β-D-glucans with degrees of polymerization of 25-31 and various high-M(r), substituted and side-branched fungal (1→3;1→6)-β-D-glucans. However, the isoenzymes differ in their rates of hydrolysis of a (1→3;1→6)-β-D-glucan from baker's yeast and their specific activities against laminarin vary significantly. The enzymes do not hydrolyse (1→3;1→4)-β-D-glucans, (1→6)-β-D-glucan, CM-cellulose, insoluble (1→3)-β-D-glucans or aryl β-D-glycosides.
Structure type: homopolymer ; n is large
Location inside paper: p.455, table 1
Trivial name: β-1,3-glucan, pachyman, curdlan, SSG
Compound class: EPS, glucan, cell wall glucn, cell wall glucan, cell wall glucoprotein
Contained glycoepitopes: IEDB_1397514,IEDB_142488,IEDB_146664,IEDB_153543,IEDB_158555,IEDB_161166,IEDB_2278476,IEDB_2278477,IEDB_558869,IEDB_857743,IEDB_983931,SB_192
Methods: enzymatic digestion, ion-exchange chromatography, enzymatic assays, gel electrophoresis, amino acid sequence analysis, isoelectric focusing, chromatofocusing
Enzymes that release or process the structure: (1-3)-a-D-glucanase isoenzymes from barley (Hordeum vulgare)
Comments, role: from curdlan, pachyman
Related record ID(s): 3459, 43323, 100208, 102752, 103899, 103956, 106265, 106269, 106270, 110076, 110100, 110138, 111873, 111972, 111976, 118123, 125281, 125854, 126051, 130953, 130960, 130963, 139820, 139829, 141508, 143679, 149482
NCBI Taxonomy refs (TaxIDs): 511,
81056Reference(s) to other database(s): GTC:G51056AN, GlycomeDB:
157, CCSD:
50422, CBank-STR:4225
Show glycosyltransferases
There is only one chemically distinct structure:
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