Depolymerisation of Human and Bovine Polymeric Collagen Fibrils

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Abstract
Bovine and human polymeric collagen fibrils were incubated at 37°C over a range of pH with a crude lysosomal enzyme preparation obtained from rat liver. Electron microscopic analysis demonstrated depolymerisation of the fibrils over the pH range 3.5 to 7.5 with the cleavage of the fibrils into short segments, followed by unwinding of the protofibrils and cleavage of the protofibrils into protofibrillar particles. The depolymerisation of polymeric collagen to soluble products was followed by hydroxyproline analysis; the pH optimum for this process was approxi- mately 4.0. The soluble depolymerisation products of bovine polymeric collagen fibrils digested at pH 4.0 were found to be native tropocollagen-like molecules which rapidly aggregated at physiological pH to form intermolecularly cross-linked native type fibrils. No soluble hydroxyproline containing products were produced by this enzyme system at physiological pH, although the cleavage of polymeric collagen fibrils could be observed at the electronmicroscopic level. Polymeric collagen fibrils obtained from human ischaemic skin exhibited a similar fragmentation pattern to the in vitro depolymerisation of polymeric collagen fibrils.