Involved in the polymorphic O-glycosylation of the serine-rich repeat protein PsrP. Catalyzes the third step in glycosylation PsrP in this bacteria. Transfers glucose from UDP-glucose to the terminal glucose moiety of already-glycosylated PsrP (using truncated substrates with PsrP SSR1-GlcNAc-Glc); the C-terminal GT-D domain is sufficient for this reaction in vitro. Also transfers galactose from UDP-galactose to the terminal glucose moiety of already-glycosylated PsrP; the C-terminal GT-D domain is also sufficient for this reaction in vitro. Activity is much higher with UDP-glucose, and the enzyme has a very marked preference for PsrP substrate that has already been modified by GlcNAc and glucose. In vitro has hydrolytic activity against UDP-galactose and to a lesser extent against UDP-glucose. Also catalyzes the fourth step in glycosylation of PsrP in this bacteria. Can transfer the sugar from both UDP-glucose and UDP-galactose to the terminal sugar moiety of PsrP-GlcNAc-Glc-Glc and PsrP-GlcNAc-Glc-Gal; the C-terminal GT-D domain is also sufficient for this reaction in vitro (using truncated substrates with glycosylated PsrP SSR1). The N-terminal GT-D domain can transfer galactose from UDP-galactose to PsrP-GlcNAc-Glc-Gal or PsrP-GlcNAc-Glc-Glc in the fourth step. Protein modification; protein glycosylation. Has an N-terminal GT8 domain and a C-terminal GT-D domain. The GT8 has very little glucose transferase activity in the third glycosylation step, but is able to transfer galactose from UDP-galactose to PsrP-GlcNAc-Glc-Gal or PsrP-GlcNAc-Glc-Glc in the fourth step. The C-terminal GT-D domain catalyzes transfer of galactose and glucose to the acceptor protein (PsrP-GlcNAc-Glc) in both the third and fourth glycosylation steps. Encoded in RD10, a pathogenicity island with an atypical GC content that is associated with invasive pneumococcal disease. Pathogenicity islands account for greater than half the genomic diversity observed between isolates (PubMed:11463916, PubMed:16861665). The main function of this island seems to be correct synthesis and export of pneumococcal serine-rich repeat protein PsrP (Probable). In the N-terminal section; belongs to the glycosyltransferase 8 family. In the C-terminal section; belongs to the GT-D family.