STUDIES ON DEXTRANS AND DEXTRANASES. 4. MECHANISM OF THE ACTIONS OF INTRA- AND EXTRA-CELLULAR MOULD HYDROLASES

Abstract

Cell extracts from Penicillium lilacinum and P. funiculosum, grown on Streptococcus bovis dextran, contain an enzyme that hydrolyses oligo-saccharides of the isomaltose series with at least 3 glucose units. The effect of the presence of (1 [forward arrow] 3)-branch linkages on the hydrolysis is discussed. The failure of the extracts to hydrolyse the smallest oligosaccharides produced by the action of the extracellular endodex-tranases of P. lilacinum (dextranase A) and P. funiculosum (dextranase B) on Leuconostoc mesenteroides (Birmingham) dextran permits certain conclusions to be reached about the specificity of these enzymes. In the vicinity of the [alpha]- (1[forward arrow] 6)-branch point, which the enzymes cannot hydrolyse, several [alpha]-(1 [forward arrow] 6)-linkages of the main dextran chain are resistant to hydrolysis by the dextranases. On the reducing side of this point at least 2 adjacent linkages are resistant to hydrolysis by dextranase A or dextranase B, and on the non-reducing side of this point one adjacent linkage is resistant to hydrolysis by dextranase A. In the branched oligosaccharides produced from L. mesenteroides (Birmingham) dextran by dextranases A and B, 1 additional [alpha]-(1[forward arrow] 6)-link on the non-reducing side of the branch point is resistant to hydrolysis by both enzymes. The size of branches in L. mesenteroides (Birmingham) dextran is discussed.