Collagen cross-linking. Effect of D-penicillamine on cross-linking in vitro.
D-Pencillamine is believed to inhibit collagen cross-link biosynthesis by forming thiazolidine rings with lysyl-derived aldehydes that are intermediates in bifunctional cross-link synthesis. Recently, we showed that aldehyde biosynthesis catalyzed by lysyl oxidase occurs after the onset of fibril formation and that nascent aldehydes form Schiff-base cross-links rapidly in fibrils. This suggested that the accessibility of D-penicillamine to most aldehydes formed during cross-link synthesis might be limited. To study this, reconstituted chick bone collagen fibrils were incubated in vitro with highly purified lysyl oxidase and D-penicillamine. As reported in previous studies in vivo, allysine content increased and polyfunctional cross-link synthesis decreased with D-penicillamine. However, the concentration of bifunctional cross-links increased rather than decreased due to a 2-fold increase in N6:6'-dehydro-5,5'-dihydroxylysinonorleucine. Hydroxyallysine, an intermediate in formation of this Schiff base, decreased. A time study indicated that allysine levels increased primarily after the bulk of Schiff base synthesis. These results indicate that D-penicillamine does not inhibit bifunctional cross-link synthesis as previously suggested. Its principal effect is to block synthesis of polyfunctional cross-link products from Schiff base cross-link precursors and to cause accumulation of these precursors. This effect may be due to interference with the close molecular packing required for polyfunctional cross-link synthesis. These results also suggest a mechanism for the relative insensitivity of tissues such as bone with high hydroxylysine content to D-penicillamine. In this study, D-penicillamine caused selective accumulation of allysyl and not hydroxyallysyl residues. In bone as opposed to soft tissues, hydroxyallysyl residues are intermediates in synthesis of almost all cross-links.
D000818:Animals; D001665:Binding Sites; D001842:Bone and Bones; D002356:Cartilage; D002645:Chickens; D003094:Collagen; D006710:Homocysteine / Q000494:pharmacology; D006711:Homocystine / Q000494:pharmacology; D007700:Kinetics; D046911:Macromolecular Substances; D008715:Methionine / Q000494:pharmacology; D010396:Penicillamine / Q000494:pharmacology; D011485:Protein Binding; D008249:Protein-Lysine 6-Oxidase / Q000378:metabolism
D046911:Macromolecular Substances; D006710:Homocysteine; D006711:Homocystine; D003094:Collagen; D008715:Methionine; D008249:Protein-Lysine 6-Oxidase; D010396:Penicillamine