Enzyme Profile of the Cytoplasmic Droplet from Bovine Epididymal Spermatozoa1

Abstract

Cytoplasmic droplets have been isolated from bovine epididymal spermatozoa by centrifugation of sperm on a discontinuous sucrose gradient. Once-washed droplets are free of sperm and essentially free of contaminating soluble and particulate enzymes found in the medium which had been perfused through the distal caudal epididymis. Examination of the enzyme content of bovine cytoplasmic droplets indicates that they are rich in hydrolase enzymes which operate over a wide pH range. Droplets contain low activities of some enzymes linked to the intermediary metabolism of carbohydrates but appear to be metabolically inert organelles. High levels of hydrolase activity are also found in a particle-free supernatant of the medium which had been perfused through the epididymis. This fraction contains low levels of enzymes associated with intermediary metabolism, some of which are not observed in droplets. A light particulate fraction containing small granules, vesicles, and membrane profiles has been separated from droplets. This fraction contains hydrolase activity but no enzymes associated with intermediary metabolism. The presence of a magnesium-dependent nucleotide phosphatase of high specific activity in this fraction differentiates it from droplets and particle-free supernatant. Possible interrelationships and origins of enzyme activities in these fractions are discussed.