Catalyzes the first glycosylation step in glycosphingolipid biosynthesis, the transfer of glucose to ceramide to produce glucosylceramides (GlcCer). GlcCer are known to contribute to the physical properties and physiological functions of membranes and may regulate signal transduction. Seems to be the major active form in the nematode (PubMed:19240113, PubMed:21325339). Only branched-chain sphingoid bases like 15-methylhexadecasphing-4-enine are used for generating complex sphingolipids in Caenorhabditis elegans (PubMed:7651085). Together with cgt-1, plays a role in the trafficking of proteins such as mig-14 to the cell membrane in intestinal cells (PubMed:26115433). an N-acylsphing-4-enine + UDP-alpha-D-glucose = a beta-D-glucosyl-(1<->1')-N-acylsphing-4-enine + H(+) + UDP N-acyl-15-methylhexadecasphing-4-enine + UDP-alpha-D-glucose = H(+) + N-acyl-1-beta-D-glucosyl-15-methylhexadecasphing-4-enine + UDP Lipid metabolism; sphingolipid metabolism. Expressed in pharyngeal intestinal valve, intestinal rectal valve and hypodermis. The D1, D2, D3, (Q/R)XXRW motif is a critical part of the GCS active site, involved in catalysis and UDP-sugar binding. Reduced brood size. Reduced glucosyl-ceramide content and expression at cell surface. Increased expression of sphingomyelins and sphingomyelin clustering at cell surface. Loss of function in the germline leads to defects in oocyte formation and early embryonic divisions and shortened body length. Loss of function in somatic cells may lead to L1 arrest (PubMed:19240113, PubMed:21325339). Double RNAi-mediated knockdown together with cgt-1 reduces the rate of development and restores the basolateral cell membrane localization of mig-14 in intestinal cells in a sgk-1 ok538 mutant background (PubMed:26115433). Belongs to the glycosyltransferase 2 family.