What do you mean by person? Under income tax everyone paying tax is a person whether its a company, HUF, partnership or individual etc.
I believe by person you mean an individual.
5th Letter in PAN is surname of the person and in case of other than an individual 5th letter will be first name of pan holder.
For example, PAN of Reliance Industries Ltd is AAACR5055K, in this 5th letter is R which is first letter of Reliance.