A secretory phospholipase C-like enzyme in the bovine epididymal caput

An enzyme hydrolysing the synthetic substrate p-nitrophenylphosphorylcholine was highly active in the epididymal caput and very low or absent in other parts of the bovine reproductive organs. This enzyme was also found in the secretory fluid obtained from the epididymal caput but much lower activities were encountered in cauda epididymis and seminal plasma. The enzyme displayed an optimum at pH 6.5, an Mr of about 66000, a pI value of 5.0 and was suppressed by chelating agents and reactivated by Co2+ and Zn2+. After partial purification the enzyme also showed hydrolysis of p-nitrophenyl phenylphosphonate, bis-p-nitrophenyl phosphate and hexadecanoyl-p-nitrophenylphosphorylcholine with slightly different pH optima and modifier characteristics. It is concluded that this secretory enzyme is distinct from the membrane-bound phospholipase C and may play a role in processing of the spermatozoan phospholipids during the epididymal maturation.