CALP1 is an 8-residue calcium-like peptide that interacts with an EF hand motif based on the troponin C superfamily calcium binding site. It binds to calmodulin (Kd = 88 µM) and activates phosphodiesterase in the presence of calmodulin and absence of calcium. CALP1 also acts as a cell-permeable inhibitor of calcium influx through glutamate receptor channels in cultured rat neocortical neurons thereby inhibiting excitatory cytotoxicity (IC50 = 52.48 µM) and apoptosis (IC50 = 44.78 µM). CALP1 (1 mg/kg) pretreatment prevents increases in lung alveolar inflammatory cells after six, but not 24, hours in sensitized guinea pigs challenged with ovalbumin in a model of allergic asthma. It also decreases radical production induced by phorbol 12-myristate 13-acetate in broncho-alveolar lavage cells after six and 24 hours and dose-dependently decreases histamine-induced hyperresponsiveness in isolated guinea pig tracheal rings.