The unique N-terminal sequence of testis angiotensin-converting enzyme is heavily O-glycosylated and unessential for activity or stability.
The testis-specific isozyme of angiotensin-converting enzyme (ACE) is identical, from residue 68 to the C terminus, to the second half or C-terminal domain of somatic ACE. However, the first 67 residues, comprising the signal peptide and a Ser-/Thr-rich 36-residue sequence that constitutes the N terminus of mature testis ACE, are unique. We have expressed a mutant human testis ACE lacking this 36-residue N-terminal sequence and find that compared to the wild-type protein the mutant is 15 kDa smaller due to the loss of greater than 90% of all O-linked sugars, but that it retains full enzymatic activity and is stable in culture. Heavy O-glycosylation is a property of testis ACE that is not shared by the somatic enzyme and is attributable to this unique sequence.
Ehlers
M R
MR
Center for Biochemical and Biophysical Sciences and Medicine, Harvard Medical School, Boston, MA 02115.
Chen
Y N
YN
Riordan
J F
JF
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D004795:Enzyme Stability; D015870:Gene Expression; D006031:Glycosylation; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D009005:Monosaccharides / Q000032:analysis; D007703:Peptidyl-Dipeptidase A / Q000235:genetics*; D011994:Recombinant Proteins; D012689:Sequence Homology, Nucleic Acid; D013737:Testis / Q000201:enzymology*
D000596:Amino Acids; D009005:Monosaccharides; D011994:Recombinant Proteins; D007703:Peptidyl-Dipeptidase A