Conrad Bauzon, Dom Javier and Khiel Misa starred in the Altas strong finishing kick while their defense took care of the rest en route to a 5-1 record in the eight-team tournament.
Bauzon buried back-to-back triples from the left wing while Javier completed a three-point play greeting the final two minutes of the game played before a boisterous, uniformed crowd that braved the afternoon rains.
Javiers three-point play gave Perpetual a 67-62 lead. Letran desperately stayed in the game through guards Ronjay Enrile and Boyet Bautista, 68-69, time down to 11 seconds.
After Jon Jon Refueso sank two charities in the final nine seconds, Misa sealed the victory for Perpetual when he stole off Bautista as time was running out.
The loss was the second in six games for Letran which slipped into a tie with Mapua, a 90-85 winner over Philippine Christian University in the other seniors match.
The Cardinals seemed headed to a breeze when they took an 85-62 lead but suddenly found the Dolphins swimming back to shore, 80-86. A steady finish, however, proved enough to give Mapua the victory.