Speaking about his move to east London, Perez told the club website: "I'm very happy to be here at such an historic club".
He went back to Deportivo on loan last season and was surplus to requirements at the Emirates after the arrivals of Alexandre Lacazette and Pierre-Emerick Aubameyang.
The Spaniard has teamed up with former colleague Wilshere after securing a deadline day move to join West Ham.
He has previous experience in England with Aston Villa from 2014 to 2016 and says he is looking forward to another chance having suffered relegation with Villa.
West Ham have been working on a deal to sign former Aston Villa midfielder Sanchez from Fiorentina and are close to completing the transfer.
"He is a very experienced player that Manuel and I both know well from Spain", said Husillos.
However, he would only be offered 11 Premier League appearances under Arsene Wenger, before he was sent out on loan last summer, rejoining Deportivo for the season.
West Ham United made two further signings on transfer deadline day to take their total summer spending to nearly £100 million, behind only Liverpool, Chelsea and Fulham in the entire Premier League. He scores goals, but can also create them and link well with the midfielders. "I'm very motivated." Perez said.
New Hammers manager Manuel Pellegrini has been busy since his May appointment, and Perez would represent his ninth signing since taking charge.
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