The present invention provides a new family of human proteins, designated as "Zven," as agents that stimulate gastrointestinal contractility, gastric emptying, intestinal transit, and treating gastroparesis. The Zven1 gene, which resides in human chromosome 3p21.1-3p14.3, is expressed in testicular tissue and peripheral blood lymphocytes. The invention also provides methods for using the antibodies to detect the presence of the protein with antibodies and methods for using the polynucleotides to detect the presence of Zven RNA.