that word is methionylthreonylthreonylglutaminylalanylprolylthreonylphenylalanylthreonylglutaminylprolylleucylglutaminylserylvalylvalylvalylleucylglutamylglycylserylthreonylalanylthreonylphenylalanylglutamylalanylhistidylisoleucylserylglycylphenylalanylprolylvalylprolylglutamylvalylseryltryptophylphenylalanylarginylaspartylglycylglutaminylvalylisoleucylserylthreonylserylthreonylleucylprolylglycylvalylglutaminylisoleucylserylphenylalanylserylaspartylglycylarginylalanyllysylleucylthreonylisoleucylprolylalanylvalylthreonyllysylalanylasparaginylserylglycylarginyltyrosylserylleucyllysylalanylthreonylasparaginylglycylserylglycylglutaminylalanylthreonylserylthreonylalanylglutamylleucylleucylvalyllysylalanylglutamylthreonylalanylprolylprolylasparaginylphenylalanylvalylglutaminylarginylleucylglutaminylserylmethionylthreonylvalylarginylglutaminylglycylserylglutaminylvalyl
I was gonna write the WHOLE ENTIRE WORD out but noticed I needed multiple comment to write the whole word because I did not have enough space for it in one comment and then noticed I might get reported for spam so yeah
One of the sites says . METHIONYLTHREONYLTHREONYGLUTAMINYLARGINYL … ISOLEUCINE and you can see it on https://www.mentalfloss.com/article/50611/longest-word-in-the-world