Osteoadherin (OSAD), also known as Osteomodulin, is an extracellular matrix keratan sulfate proteoglycan that belongs to the class II subfamily of small leucine-rich proteoglycans (SLRP). Leucine-rich repeat (LRR) motifs consist of approximately 20 - 30 amino acids (aa) with conserved leucine spacing, folded into a structure with one beta-sheet and one alpha-helix. OSAD contains eight sulfated tyrosine residues and is distinguished from other class II SLRPs by the presence of an approximately 70 aa C-terminal acidic domain. OSAD is expressed by fetal and adult osteoblasts but is not detectable in cartilage or tendon. In dental tissue, OSAD is expressed by odontoblasts and ameloblasts and is involved in the mineralization of bone and teeth. OSAD promotes the adhesion of osteoblasts and odontoblasts to the surrounding matrix.