I feel disappointed , Even for a such a simple thing i don't see reply. Thanks for Oracle Community
The Grants are part of the new Role Based Access Control System. In this new Security Paradigm, its not the Responsibility but role of a user in the OU.
Grants do not work without Appropriate role assignments to users. I have used the RBAC and UMX for AME.
You may refer Note 290525.1 for differences between Role and Responsibility and how grants play role in structuring the data access to a particular user.
Hope this helps.