Abstract
.gamma.-Glutamylamine cyclotransferase, an enzyme that catalyzes the conversion of L-.gamma.-glutamylamines to free amines and 5-oxo-L-proline, was found in rabbit kidney and in various other tissues. The specificity of this enzyme indicates that it functions in the metabolism of products of transglutaminase action; among its substrates are .epsilon.-(L-.gamma.-glutamyl)-L-lysine, a derivative of this peptide in which the .alpha.-amino and carboxyl groups of the lysine moiety are blocked, and L-.gamma.-glutamylpolyamine derivatives.