Alter Privilege

You can revoke the Alter privilege on a sequence from another user, from PUBLIC, or from a role. The Alter privilege enables a specified user or role to modify the definition of a sequence with the ALTER SEQUENCE statement or to rename the sequence with the RENAME SEQUENCE statement.

The following REVOKE statement cancels any Alter privilege that was granted individually to user mark on the cust_seq sequence object: 
REVOKE ALTER ON cust_seq FROM mark;