..., we examined aged human lenses and found several proteins to be crosslinked at Glu and Gln residues. This new covalent bond involves the amino group of Lys or an α-amino group. A number of these crosslinks were found in intermediate filament proteins. Such crosslinks could be reproduced experimentally...

...Michael G. Friedrich; Zhen Wang; Kevin L. Schey; Roger J. W. Truscott Long-lived proteins (LLPs) are present in numerous tissues within the human body. With age, they deteriorate, often leading to the formation of irreversible modifications such as peptide bond cleavage and covalent cross-linking...

... in cleavage in the IGD of immature aggrecan, for both the bovine and the human substrates. Both aggrecanases showed a similar ability to cleave within the CS2 domain of bovine aggrecan irrespective of age, but showed a much lower ability to cleave within the CS2 domain of human aggrecan. Equivalent results...