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Journal of Biochemistry Advance Access published online on November 4, 2008
Journal of Biochemistry, doi:10.1093/jb/mvn148
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© The authors 2008. Published by Oxford University Press on behalf of the Japanese Biochemical Society. All rights reserved.

Testicular Angiotensin-Converting Enzyme with Different Glycan Modification: Characterization on Glycosylphosphatidylinositol-Anchored Protein Releasing and Dipeptidase Activities

Gen Kondoh1,2,*, Hitomi Watanabe1, Yuko Tashima3, Yusuke Maeda3 and Taroh Kinoshita2,3,4

1Laboratory of Animal Experiments for Regeneration, Institute for Frontier Medical Sciences, Kyoto University, Kyoto 606-8507, Japan
2 CREST Program, Japan Science and Technology Society, Kyoto, Japan
3 Department of Immunoregulation, Research Institute for Microbial Diseases, Suita 565-0871, Osaka, Japan
4 Laboratory of Immunoglycobiology, Immunology Frontier Research Center, Osaka University, Suita 565-0871, Osaka, Japan

*To whom correspondence should be addressed: Dr. Gen Kondoh. Laboratory of Animal Experiments for Regeneration, Institute for Frontier Medical Sciences, Kyoto University. 53 Syogoin-Kawahara-cho, Sakyok-ku, Kyoto 606-8507, Japan. Tel/Fax: +81-75-751-4860, E-mail address: kondohg{at}frontier.kyoto-u.ac.jp

Received August 10, 2008; Accepted October 23, 2008


  Abstract

We have previously found that the angiotensin-converting enzyme (ACE) carries GPI-anchored protein releasing activity (GPIase) as well as dipeptidase activity. Testicular ACE (tACE), the male germinal specific isozyme, plays a crucial role in male fertilization. The amino-terminal region of this isozyme is different from that of somatic isozyme (sACE) and contains potential O-linked glycosylation sites. By multiple mutagenesis after an in silico prediction, amino acid residues acquiring O-glycans were assigned. Both GPIase and dipeptidase activities were compared between O-glycan null mutant and wild-type molecules, but no differences were found. Furthermore, the wild-type tACE was produced in two different cells (COS7 and CHO) and its activities compared. The GPIase activity, but not dipeptidase, was apparently higher for CHO-derived molecule than COS7. Sensitivity to neuraminidase and O-glycosidase digestions and the profile of glycosylation were quite different between these two molecules. Moreover, serial digestions with neuraminidase and O-glycosidase have no influence on GPIase activity of both molecules, suggesting that the sialylation and the presence of O-glycan has no influence on tACE enzyme activities, while the set of glycans modulate GPIase activity.

Key Words: angiotensin-converting enzyme, enzyme activity, glycan, gpi-anchored protein, post-translational modification


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