a beta-D-Gal-(1->4)-beta-D-Glc-(1<->1)-Cer(d18:1(4E)) + CMP-N-acetyl-beta-neuraminate = N-acetyl-alpha-neuraminyl-(2->6)-beta-D-galactosyl-(1->4)-beta-D-glucosyl-(1<->1)-ceramide + CMP + H(+) — reaction