Sperm express a Ca 2+}-regulated NAADP synthase

Sridhar R Vasudevan , Antony Galione , Grant C Churchill (1)

1 Pharmacology

NAADP (nicotinic acid adenine dinucleotide phosphate), the most potent Ca 2+}-mobilizing second messenger, is active in a wide range of organisms and cell types. Until now, all NAADP producing enzymes have been thought to be members of the ADP-ribosyl cyclase family. ADP-ribosyl cyclases exhibit promiscuous substrate selectivity, synthesize a variety of products and are regulated in a limited manner, which may be non-physiological. We now report the presence of an enzyme on the surface of sea urchin sperm that exhibits bell-shaped regulation by Ca 2+} over a range (EC 50} of 10 nM and IC 50} of 50 µM) that is physiologically relevant. Uniquely, this surface enzyme possesses complete selectivity for nucleotides with a 2'-phosphate and exhibits only base-exchange activity without any detectable cyclase activity. Taken together, these findings indicate that this novel enzyme should be considered as the first true NAADP synthase.

Mots clés: Life Sciences

Sridhar R Vasudevan, Antony Galione, Grant C Churchill. Sperm express a Ca 2+}-regulated NAADP synthase. Biochemical Journal, 2008, 411 (1), pp.63-70. ⟨10.1042/BJ20071616⟩. ⟨hal-00478929⟩