Adenosine 3'5'-monophosphate phosphodiesterase of buffalo spermatozoa

Publisher Website
Google Scholar
Abstract
The cyclic(c)AMP-phosphodiesterase (EC 3.1.4.17) of buffalo spermatozoa is distributed in the head, mid-piece and tail fractions and has multiple forms, 70% of which is in the bound form. The bound enzyme was not solubilized by Triton X-100, lubrol or hyamine 2389. Kinetic measurements of the soluble enzyme showed 2 apparent Km values for low and high cAMP concentrations, i.e., 4.5 and 100 .mu.M with Vmax values of 0.25 and 2.0 nmol cAMP hydrolyzed min-1 mg protein-1. The bound enzyme had an apparent Km of 66.6 .mu.M with a Vmax of 0.75 nmol cAMP hydrolysed min-1 mg protein-1. The pH for optimum enzyme activity was 7.5 and Mg2+ was essential for the activity of the soluble and bound enzymes. Methylxanthines, ATP, ADP and PPi [inorganic phosphate] inhibited the soluble and bound enzymes, ATP being the most potent inhibitor.