Comparative studies on collagen glycosylation in chick skin and bone

Abstract

Glycosiylation has been examined in Type I collagens from chick skin and bone in situations where the amount of hydroxylysine in these collagens is known to vary. The following observations were made. 1. 1. The age-dependent decrease in the hydroxylation of lysine known to occur in both α1- and α2-chains, mostly in the immediate post-embroyonic peiod, was found to coincide with a reduction in these chains in the level of glycosylation which fell from approximately nine glycosylated residues per molecule in skin and seven in bone to a relatively constant value, in each, approaching four. 2. 2. The ratio of glucosylgalactosyl- to galatocylhydroxylysine remained generally in the region of two in bone but declined with age to a value of unity or less in skin. 3. 3. Increased hydroxylation in bone collagen in calium deficiency equivalent to 5–6 residues of hydroxylysine per chain, was accompanied by an increase in glycosylation amounting only to about one-half residue per chain. There was no change in the ratio of di- to monosaccharide substitution. 4. 4. The relatively high degree of hydroxylation in embryonic collagens of the lysyl residue located in the N-terminal, non-helical telopeptide region of the α1 (I)-chain was associated with only minimal glycosylation. The significance of these findings is discussed and in particular it is concluded that there is no readily-discernible, tissue-dependent pattern of glycosylation that could indicate a role for the latter in calcification for example.