Mohammed signed a five-year contract with the capital-based outfit in a deal worth €9 million.
The attacking midfielder passed his mandatory medicals on Thursday morning before putting pen to paper to conclude the deal to the Dutch Eredivisie where he has been given the number 20 jersey.
According to Jansen, who works with Voetbal International, the 19-year-old was acquired as a replacement for Van de Beek.
The Dutch midfielder has been linked with several European elite sides including Real Madrid and Manchester United.
"It is a dynamic player, who especially should be able to manage as number ten," says Jansen . "That makes it interesting, because Donny van de Beek is of course the number ten of Ajax at the moment. There is still a very good chance that he will leave this summer. Then you have a potential replacement with Kudus."
Mohammed has been one the most prolific teenagers in Denmark, plundering 12 goals in 25 appearances for Nordsjælland.