The Notorious B.I.G. estate wasted no time threatening Kendall and Kylie Jenner with a lawsuit if they don't put a stop to selling shirts with the legendary rapper's image.

The estate's lawyer, Julian K. Petty, fired off a cease and desist letter to the J sisters with a deadline of 5 PM Friday to stop pimping the shirts ... or face a lawsuit.

It appears the letter was effective -- hours after Petty sent it ... the Biggie shirt -- along with 2 others featuring Tupac's image -- was no longer available on the website.

The estate's adamant it NEVER gave the Jenners permission, and Petty tells us, "This is misappropriation at its finest. I’m curious to hear the justification. I’m even more curious to hear the proposed resolution."

As we reported ... Biggie's mom, Voletta Walace, said ripping her son's image to sell t-shirts on the girls' website is "disrespectful and exploitation at its worst." 

We've reached out to the Jenners, so far no word back.