Chemical and Functional Properties of Mutastein, an Inhibitor of Insoluble Glucan Synthesis by Streptococcus sobrinus

Mutastein, a potent inhibitor of insoluble glucan synthesis by Streptococcus sobrinus, is a protein with a molecular weight of ~ 2 × 106. Amino acid and ELISA analyses suggested that mutastein is a mixture of heterogenous polymers of α-casein contained in the culture medium of the producing strain, Aspergillus terreus M3328. Mutastein strongly inhibited the primer-dependent insoluble glucan synthase of S. sobrinus B13. The primer-independent soluble glucan synthase was not affected by mutastein while primer-dependent soluble glucan synthase was slightly activated.