Chemical and Structural Composition of Alpaca (Vicugna pacos) Skin with a Focus on Collagen Crosslinks

Alpacas (Vicugna pacos) produce a high-value fibre and leather that is increasingly sought after for the production of luxury goods. Although several studies have addressed the genetics and gene expression of alpaca skin, particularly those associated with colour, little is known about the structural and molecular compositions of alpaca skin. In this study, alpaca skin was analysed using small angle X-ray scattering (SAXS), analytical and physical methods. Using SAXS, the axial periodicity (65.1 nm) and intermolecular lateral packing distance (1.47 nm) of collagen in alpaca skin are determined to be similar to the previous studies on skins from other animal species. The collagen crosslinking profile in alpaca skin shows the presence of six crosslinks including pyridinoline and deoxypyridinoline and this is different from other animal skins. We hypothesised that the biosynthesis of pyridinoline and deoxypyridinoline in biological tissues is driven by a combination of several factors including amino acid sequence of collagen type I and lysyl hydroxylase activity. In this work, we showed that alpaca skin collagen crosslinks are diverse and their relative concentrations are different from other animal skins. We also detected histidinohydroxylysinonorleucine crosslink in alpaca skin which lacks histidine in its C-terminal telopeptide of type I collagen.