Hemoprotein Nitric Oxide Synthase in Aplysia Californica

Nitric oxide (NO) plays a crucial role in neuronal signaling in a variety of eukaryotic and prokaryotic organisms. Nitric oxide synthases (NOS) are heme-containing monooxygenases that catalyze the oxygen dependent oxidation of L-arginine to NO and L-citrulline. The NO produced by NOS activity is a gaseous molecule that diffuses easily through membranes and acts inter or intracellularly. NO activates metal-containing enzymes, including soluble guanylate-cyclase (sGC) that increase levels of the messenger molecule cyclic 3,5-guanosine monophosphate (cGMP) (1, 2) which in turn mediate various pathophysiological or physiological functions in neurons. Nevertheless, many aspects of nitrergic neurons and NO function in the central nervous system (CNS) are unclear. The aim of research described in this thesis was to characterize neuronal NOS, proteins metabolically linked to NOS and NO signaling pathways in the CNS of Aplysia cali/ornica (Aplysia), a popular experimental model in cellular and system neuroscience. The biochemical characteristics of Aplysia NOS (AcNOSj described here revealed its calcium-/calmodulin-(Ca/CaM) and NADPH dependence. A representative set of inhibitors for mammalian NOS isoforms also suppressed NOS activity in Aplysia Polyclonal anti-rat nNOS antibodies hybridized with a putative purified..