Virulence factor (By similarity). Involved in the degradation of glycogen of the mammalian host cells (PubMed:21565699). Hydrolyzes the alpha-1,6-branchpoints of glycogen (PubMed:20497336, PubMed:21565699). Hydrolyzes pullulan. Does not hydrolyze dextran (PubMed:20497336). Binds to mouse lung alveolar type II cells that are rich in glycogen stores. Is an alpha-glucan-specific carbohydrate-binding protein, which binds to amylose (pure alpha-(1,4)-linked glucose), amylopectin (alpha-(1,4)-linked glucose with alpha-(1,6) branch points), pullulan (linear polymer of mixed alpha-(1,4)- and alpha-(1,6)-linked glucose) and glycogen (similar to amylopectin with more frequent alpha-(1,6) branch points) in vitro. Does not bind to dextran (a linear polymer of alpha-(1,6)-linked glucose) (PubMed:17187076). Hydrolysis of (1->6)-alpha-D-glucosidic linkages in pullulan, amylopectin and glycogen, and in the alpha- and beta-limit dextrins of amylopectin and glycogen. Inhibited by 4-O-alpha-D-glucopyranosylmoranoline (G1M). kcat is 270 min(-1) for pNP-M5. Localizes to cytoplasm in the lung alveolar type II cells of the mouse and human hosts. The N-terminal tandem family 41 carbohydrate-binding modules (CBM) are involved in carbohydrate binding (PubMed:17187076, PubMed:21565699). The C-terminal glycosyl hydrolase 13 (GH13) domain is involved in catalysis (PubMed:21565699). Grows readily on glucose and maltotriose, but not on glycogen. No soluble alpha-glucooligosaccharides detected in the culture supernatant. This protein may have potential in the disruption of glycogen adherence of the pneumococci to the host cell or disruption of glycogen breakdown in the host cells by the bacteria and thus could be useful in treating streptococcal lung infections. Belongs to the glycosyl hydrolase 13 family.