 Additionally, CRMPs are homologs of Unc33 whose mutation causes impaired ability to form neural circuits and uncoordinated mobility in "Caenorhabditis elegans".CRMP1-4 genes are roughly 60% homologous with the tetramer liver dihydropyrimidinase (DHPase), and also possess a similar structure to members of the metal-dependent amidohydrolases.However, the fact that CRMPs are not enzymatic reveals that they might lack the critical "His" residues that are present in amidohydrolase enzymes to allow them to bind metal atoms to their active site.