Nucleoside 3′,5′-Monophosphate Phosphodiesterases in Sea Urchin Sperm1

Abstract

In sea urchin sperm, the hydrolysis of adenosine 3',5'-monophosphate (cyclic AMP) appears to be predominantly catalyzed by a protein different from that which catalyzes the hydrolysis of guanosine 3',5'-monophosphate (cyclic GMP). The cyclic GMP phosphodiesterase is located primarily in the particulate fraction, whereas the cyclic AMP phosphodiesterase is found mainly in the soluble fraction of the sperm cell homogenate. The cyclic AMP and cyclic GMP phosphodiesterases are inactivated at different rates by N-ethylmaleimide and are inhibited to different degrees by various phosphodiesterase inhibitors. Three fractions (A, B, C) of cyclic nucleotide phosphodiesterase activity (as measured at 1 µM substrate) can be separated by DEAE-cellulose chromatography of the supernatant fraction. The bulk of the recovered cyclic AMP phosphodiesterase activity is found in fraction C while most of the recovered cyclic GMP phosphodiesterase activity is contained in fraction B.