Required for sperm motility, function and male fertility. May be involved in the normal assembly of the sperm fibrous sheath and provides most of the enolase activity in sperm (PubMed:23446454). (2R)-2-phosphoglycerate = H2O + phosphoenolpyruvate Carbohydrate degradation; glycolysis; pyruvate from D-glyceraldehyde 3-phosphate: step 4/5. Interacts with ENO1 (PubMed:23446454). Isoform 1 and isoform 4 interact with AKAP4 (PubMed:23446454). Testis-specific (PubMed:23446454, PubMed:32248064). Expressed in spermatids and ependyma (at protein level) (PubMed:32248064). Expressed at higher levels in late spermatids than in pachytene spermatocytes. Expressed at higher levels in pachytene spermatocytes than in late spermatids. Synthesized as an approximately 70-kDa precursor, which then undergoes proteolytic cleavage to an approximately 60-kDa enzyme; HOATZ associates directly or indirectly with ENO4 to mediate this process before its transport to mature flagella. Male mice are infertile and the sperm have significantly reduced motility, ATP levels, and enolase enzymatic activity as well as a structurally abnormal sperm fibrous sheath. Belongs to the enolase family. Although it belongs to the enolase family, Leu-362 is present instead of the conserved Glu which is expected to be an active site residue. Truncated N-terminus. Truncated N-terminus.