Studies on Chitin IV. The Occurrence of Complexes in Which Chitin and Protein are Covalently Linked

Abstract

Samples of chitin have been prepared from the cuticles of insects and crustacea, from cuttlefish shell, and from the skeletal pen of squid. In every case protein was bound by covalent bonds to the chitin so forming stable complexes (glycoproteins). Glycoproteins from different sources contained differing amounts of chitin and protein, the ratio of chitin to protein varying from 1 : 1 to 20 : 1. The protein would appear to be linked to the chitin through aspartyl or histidyl residues or both and each glycoprotein is polydisperse. The chitin preparations included glycoproteins which contained a;- and {3-type chitina and also a third and different type of chitin. The amino acid composition of the protein components of the glycoproteins has been determined. It ia probable that chitin does not occur uncombined with protein.