Angiotensin-converting enzyme: structural relationship of the testicular and the pulmonary forms

Angiotensin-converting enzyme exists in two isozymic forms that are encoded by two mRNAs. Recently, the complete primary structures of the testicular isozymes from rabbit and human and of the pulmonary isozymes from mouse and human have been determined. We report here the cloning of a portion of the cDNA for the rabbit pulmonary isozyme by using the polymerase chain reaction. The sequence of this cDNA was identical to the sequence of the corresponding portion of rabbit testicular cDNA. This observation suggests that the two mRNAs are transcribed from the same gene. Comparison of the structures of the enzyme isolated from different species is useful for identifying the functional constraints on the evolutionary changes of its structure.