Is there is a way to Import/Retrieve Keypair from Public Key?

[root123-bot]

I'm currently facing the challenge about this module, I've created keyPair and I want to POST these keyPair object to another endpoint, what I facing now is that after JSON.parse the stringified KeyPair object it miss raw data of original keyPair which can be used to sign and verify data, after posting it to another endpoint all I have is hexadecimal public key and now I want to retrieve the original/initial created KeyPairs from this hexadecimal public key. So my Question is, there is a way to retrieves the keyPair I've created using hexadecimal public key for me to be able to sign and verify data?
Your help will be appreciated...
Thanks