Mice heterozygous for a null mutation of CPE show reduced expression of carboxypeptidase e mRNA and enzyme activity but normal physiology, behavior, and levels of neuropeptides

•CpeNeo/Neo mice do not express carboxypeptidase E, an important neuropeptide processing enzyme.•Homozygous CpeNeo/Neo mice have greatly reduced levels of most neuropeptides and are overweight, subfertile, anxious, and depressed.•Heterozygous CpeNeo/+ mice have ∼ 50% reduced expression of CPE mRNA and greatly reduced enzyme activity.•Heterozygous CpeNeo/+ mice are identical to wild-type mice in terms of neuropeptide levels, physiology and behavior, indicating that CPE is not a rate-limiting enzyme.