PP1γ1 is unable to substitute for the mammal-specific PP1γ2 isoform to support male fertility and sperm function.

The serine-threonine phosphatase has four paralogs - PP1α, PP1β, PP1γ1 and PP1γ2 - encoded by three genes, Ppp1ca, Ppp1cb, and Ppp1cc. Protein phosphatase PP1γ2, one of two isoforms of the gene Ppp1cc, is expressed in spermatogenic cells in testis and sperm, while PP1γ1 is found in somatic cells. The two PP1γ isoforms, formed by alternate splicing which occurs only in mammals, are identical except at their C-termini.