The Cyclic AMP Phosphodiesterase of Bovine Spermatozoa: Multiple Forms, Kinetic Properties and Changes during Development,

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Abstract
The cyclic AMP phosphodiesterase of bovine sperm from the caudal and caput epididymidis has been shown to contain 5 seperate enzymic forms. Approximately one-half (49.1 ± 1.8%) and two-thirds (69.8 ± 1.7%) of the enzyme is particulate in caput and caudal cells respectively. This particulate form, as well as 4 additional soluble forms separable by preparative isoelectric focusing or molecular sieving techniques, all display anomalous kinetic behavior with downwardly sloping Lineweaver-Burke plots. We have determined "limiting Km" values for all forms and have shown these to be comparable for both cell types. The isoelectric points (3.9, 4.1, 4.6 and 5.0) of the 4 focused forms of the 2 cell types are also nearly identical. Molecular weights of the soluble forms of caudal spermatozoa are 22,000, 170,000, 300,000 and ≥400,000 daltons.