Methionylglutaminy...serine is a scientific name for tryptophan synthetase, which is made up of 267 amino acids. It has appeared written down a number of times and has 1913 letters.

According to the Guinness Book of World Records, 18th edition, it is the longest chemical word for C₁₂₈₉H₂₀₅₁N₃₄₃O₃₇₅S₈.

Lots of much larger proteins exist and their "scientific names" can be written in the same way. If nobody has actually bothered to write down such a scientific name, it is a fine metaphysical point whether the names should be said to exist, and if not, whether this particular string of letters representing a rather average, modest-sized protein is better qualified to be called a "word".

The full name, containing 1913 letters (excluding any dashes), is:

methionylglutaminylarginyltyrosylglutamylserylleucylphenylalanylalanyl-

glutaminylleucyllysylglutamylarginyllysylglutamylglycylalanylphenylalanyl-

valylprolylphenylalanylvalylthreonylleucylglycylaspartylprolylglycyl-

isoleucylglutamylglutaminylserylleucyllysylisoleucylaspartylthreonylleucyl-

isoleucylglutamylalanylglycylalanylaspartylalanylleucylglutamylleucyl-

glycylisoleucylprolylphenylalanylserylaspartylprolylleucylalanylaspartyl-

glycylprolylthreonylisoleucylglutaminylasparaginylalanylthreonylleucyl-

arginylalanylphenylalanylalanylalanylglycylvalylthreonylprolylalanyl-

glutaminylcysteinylphenylalanylglutamylmethionylleucylalanylleucyl-

isoleucylarginylglutaminyllysylhistidylprolylthreonylisoleucylprolyl-

isoleucylglycylleucylleucylmethionyltyrosylalanylasparaginylleucylvalyl-

phenylalanylasparaginyllysylglycylisoleucylaspartylglutamylphenylalanyl-

tyrosylalanylglutaminylcysteinylglutamyllysylvalylglycylvalylaspartylseryl-

valylleucylvalylalanylaspartylvalylprolylvalylglutaminylglutamylseryl-

alanylprolylphenylalanylarginylglutaminylalanylalanylleucylarginylhistidyl-

asparaginylvalylalanylprolylisoleucylphenylalanylisoleucylcysteinylprolyl-

prolylaspartylalanylaspartylaspartylaspartylleucylleucylarginylglutaminyl-

isoleucylalanylseryltyrosylglycylarginylglycyltyrosylthreonyltyrosylleucyl-

leucylserylarginylalanylglycylvalylthreonylglycylalanylglutamylasparaginyl-

arginylalanylalanylleucylprolylleucylasparaginylhistidylleucylvalylalanyl-

lysylleucyllysylglutamyltyrosylasparaginylalanylalanylprolylprolylleucyl-

glutaminylglycylphenylalanylglycylisoleucylserylalanylprolylaspartyl-

glutaminylvalyllysylalanylalanylisoleucylaspartylalanylglycylalanylalanyl-

glycylalanylisoleucylserylglycylserylalanylisoleucylvalyllysylisoleucyl-

isoleucylglutamylglutaminylhistidylasparaginylisoleucylglutamylprolyl-

glutamyllysylmethionylleucylalanylalanylleucyllysylvalylphenylalanylvalyl-

glutaminylprolylmethionyllysylalanylalanylthreonylarginylserine

See also

• longest word in the English language.