I have known for a long time that pawpaw is used as a meat tenderizer and have read that pawpaw contains the proteolytic enzyme (papain) but the tray appeared to contain just grease (fat) which is a different molecule to protein. I have tried to find out more from the Internet but have come across more nonsense than sense.
In the early 1990s I was told a story (possibly an urban myth) about a friend of a friend who consumed pawpaw and water only for sometime and ended up in hospital with a dissolving stomach. I believe we have some biochemists among us so I'm hoping that they know whether papain is a lipase as well as a proteolytic enzyme and/or more about paw-paw enzymes and what they catalyse.
Ref: Tirsha Raynlyn
“The method of changing the sex of the male pawpaw tree by cutting it down to about three feet off the ground was accidentally proved in a garden at Milton this season.
The owner cut down three male trees and inserted a female shoot on top of each. Owing probably to the very dry weather all these shoots died and two of the trees were rooted out. The third was left and it sent out two strong shoots about a foot below the top. These shoots bore female flowers and three fruits matured one of them remaining on the tree last May as shown in the accompanying illustration.”