Hydroxyproline is a major component of the protein collagen, found only in mammalian collagen and elastin, but also present in several other proteins in plants. Hydroxyproline accounts for about 4% of all amino acids found in animal tissues and plays an important role in collagen stability. Hydroxyproline, which is hydrolyzed in tissues, is an indicator of the amount of collagen or gelatin directly. PicoSens™ Hydroxyproline Assay Kit can easily and easily measure hydroxyproline in tissues or proteins and peptide hydrolysates at absorbance (OD = 560 nm).