486 does not have 155 or 310-025 as a pre-requisite, however, 486 is not in itself a certification (you get a score report, but no certificate).
486 is part of jCert, or if you prefer, part of a websphere or VisualAge certification. For the certification (whichever one you choose) you need to pass:
486
SCJP2
Your choice of
IDE or other eligable exam
James