Program automation/global application...please help

I need to perform the following sequence of commands on 400000 files.

gunzip ; perl -pi -e 's/YSN/LYS/g' ; gzip

Each of the 400000 files is in its own subdirectory. Each file has a similiar desgination as follows.

./aa#/prod/#/#/final.pdb.gz

So for example one of the files could be ./aa1/prod/50/0/final.pdb.gz .

I dont know if this would help, but I can put all the file names into a list in a file.

I am a novice at programming, however I know there must be a way to automate this. Someone please help. I am using linux red hat.