Lipase I (LIPI)

The deduced 460-amino acid protein contains a hydrophobic leader sequence with a putative cleavage site after amino acid 15, a central lipase consensus sequence, a central 12-amino acid lipase lid sequence, and several conserved cysteines. The GxSxG sequence includes the active site ser159, which forms a putative catalytic triad with asp183 and his258. LPDL shares 71% amino acid identity with mouse Lpdl, 44% identity with LPDLR, and 34% identity with phospholipase PLA1A. Northern blot analysis of several human and mouse tissues detected strong expression of a 2.0-kb transcript only in testis. In situ hybridization of 2-week-old mice detected Lpdl expression in testis, with weaker expression in hepatocytes. In testis of adult mice, Lpdl was expressed in the cytoplasm of primary spermatocytes, but not in mature sperm or in Leydig cells.