Probable inactive glycosyltransferase required during spermatid development. May participate in protein loading into the acrosomes and accumulation of ubiquitin-proteasome systems around the head-tail coupling apparatus region. Localizes to the juxtanuclear region, possibly the late endosome. Not localized in the Golgi apparatus in round spermatids (By similarity). Mainly expressed in testis. Weakly or not expressed in other tissues. There are two conserved domains in the glycosyltransferase region: the N-terminal domain (domain A, also called GT1 motif), which is probably involved in manganese coordination and substrate binding and the C-terminal domain (domain B, also called Gal/GalNAc-T motif), which is probably involved in catalytic reaction and UDP-Gal binding. Defects in GALNTL5 have been found in a patient with primary infertility due to asthenozoospermia. Belongs to the glycosyltransferase 2 family. GalNAc-T subfamily. In contrast to other members of the family, lacks the C-terminal ricin B-type lectin domain, which contributes to the glycopeptide specificity. No glycosyltransferase activity has been detected in an in vitro assay (PubMed:24398516). Putative polypeptide N-acetylgalactosaminyltransferase-like protein 5