Catch-relaxing peptide (CARP) is isolated from Mytilus edulis (blue mussel). This peptide has a significant role in the regulation of muscle contraction. The peptide exhibits potentiating (contraction) and inhibitory (relaxation) effects on the anterior byssus retractor muscle.Mussel: H-Ala-Met-Pro-Met-Leu-Arg-Leu-NH2 or H-AMPMLRL-NH2