The novel protein p33MONOX (p33Monooxygenase) was over-expressed in neuroblastoma cells demonstrating its inhibitory effect on the phosphorylation of the App (amyloid precursor protein) and Bcl2 (B-cell lymphoma 2) proteins but mediating higher activation of Mapk1/3 (mitogen-activated protein kinase 1/3). We employed a variety of cell biology techniques to show the localization of p33MONOX to the cytoplasm of pyramidal neurons in the mouse brain hippocampus. We also carried out a yeast-two-hybrid screening plus co-immunoprecipitation and bio-informatics to determine COBRA1 (cofactor of BRCA1 (breast cancer type 1)), NOL12 (nucleolar protein 12), and PRNP (prion protein) as p33MONOX-interacting proteins. Bio-computational analyses revealed a flavine-containing monooxygenase (FMO)-1 motif, thus linking p33MONOX to a group of previously characterized proteins, the MICALs (molecule interacting with CasL). Concluding, p33MONOX might regulate pre- and post-transcriptional control of dynamic processes related to growth cone guidance.