Antiporter that transports nucleotide sugars across the endoplasmic reticulum (ER) membrane in exchange for another nucleotide sugar. May couple UDP-alpha-D-glucuronate (UDP-GlcA) or UDP-alpha-D-xylose (UDP-Xyl) efflux to UDP-alpha-D-glucuronate (UDP-GlcA) influx into the ER lumen, which in turn stimulates glucuronidation and excretion of endobiotics and xenobiotics. ; [Isoform 1]: Has UDP-GlcA:UDP-GlcNAc antiporter activity. ; [Isoform 2]: Has UDP-GlcA:UDP-GlcNAc antiporter activity.
