Purification and properties of a (1 -> 6)-beta-glucanase from Acremonium sp IMI 383068

Several isolates of Acremonium sp. grew well on pustulan, a (1 -->6)-beta - glucan, as sole carbon source and produced extracellular pustulan degrading enzymic activity. The extracellular enzymic activity of Acremonium sp. IMI 383068 against pustulan was due to the synthesis of a single (1 -->6)-beta -glucanase, which was purified to homogeneity by FPLC. The molecular weigh t of this enzyme tvas estimated by SDS-PAGE to be 41.2 kDa. The enzyme is n on-glycosylated with a pi of 4.5. It hydrolysed pustulan and lutean, both ( 1 -->6)-beta -glucans, with a lower activity against lutean, and Eisenin bi cyclis laminarin, a (1 -->3)(1 -->6)-beta -glucan. Other substrates examine d gave little or no detectable activity. TLC analyses of degradation produc ts from enzymic digests of pustulan were consistent with the (1 -->6)-beta -glucanase, having an endo-hydrolytic mode of attack and it may be classifi ed as glucan (1 -->6)-beta -D-glucan glucanohydrolase CEC 3.2.1.75]. N-term inal sequence [SWIS-PROT P82788] analysis and BLAST searching revealed only a low level (ca 50%) of amino acid homology with the (1 -->6)-beta -glucan ase from Trichoderma harzianum, the only other fungal (1 -->6)-beta -glucan ase sequence contained in the data base. Furthermore, this homology was onl y revealed after alignment of the Acremonium sp. IMI 383068 sequence starti ng at amino acid 45 of the T. harzianum sequence, suggesting that the first 44 amino acids were missing from the Acremonium (1 -->6)-beta -glucanase. The possible reasons for this are discussed. Homology was also seen with N- terminal amino acid sequences of several fungal (1 -->3)-beta -glucanases. (C) 2001 Elsevier Science Inc. All rights reserved.