i found a bigger word
Methionylthreonylthreonylglutaminylarginyltyrosylglutamylserylleucy.....minylserylglutamylasparaginylglutaminylglutaminylserxisoleucine
is the name of titin (the largest protein) , this consists of 189819 letters
go here to see the full name : https://www.digitalspy.com/fun/a444700/longest-word-has-189819-letters-takes-three-hours-to-pronounce/