The evolution of the endozepine-like peptide (ELP) in the mammalian testis

The endozepine-like peptide (ELP) is a testis-specific isoform of the acyl-CoA binding protein (ACBP) and shares the latter's peptide motif for binding mid-long chain acyl-CoA groups. ELP is expressed both as mRNA and protein at high levels in the testes of a wide range of mammals, including rodents, carnivores and ruminants. However, the ELP gene is progressively inactivated through primate evolution, with no protein detectable in a range of primates studied, including human. In nonprimate species, ELP is expressed in very late postmeiotic germ cell stages only, such that its function in these species is probably associated with the metabolism of the mature spermatozoon. Current research is looking at both the function of the ELP protein and the haploid regulation of the gene.