Amino acids in different layers of the matrix of the normal equine hoof. Possible importance of the amino acid pattern for research on laminitis.

A method was developed for separating different layers of the matrix of the equine hoof wall by dissection, and the layers were then analyzed with respect to their amino acid composition. The results were used to compare the biochemistry of hard keratinization (e.g., in the hoof wall matrix) and soft keratinization (e.g., in the epidermis of the skin). Hard keratinization differed from soft keratinization not only by its previously well known high incorporation of cystine, but also by considerable incorporation of tyrosine and threonine into the outer layers of the keratogenous zone and by the absence of increasing histidine incorporation in those layers. The importance of the results for research on the pathogenesis of laminitis is discussed.