Catalyzes the final step in the biosynthesis of the membrane lipid glucosylceramide (GluCer), the transfer of glucose to ceramide. Glucosylceramides play important roles in growth, differentiation and pathogenicity. Essential factor in determining the success of fungal infection by regulating survival of yeast cells during the initial colonization of the host lung. an N-acylsphing-4-enine + UDP-alpha-D-glucose = a beta-D-glucosyl-(1<->1')-N-acylsphing-4-enine + H(+) + UDP Lipid metabolism; sphingolipid metabolism. The D1, D2, D3, (Q/R)XXRW motif is a critical part of the GCS active site, involved in catalysis and UDP-sugar binding. Results in complete loss of glucosylceramides (GluCers) in mutant cells. Belongs to the glycosyltransferase 2 family.