Gamma-carboxyglutamate in normal and pathological human middle ear bones.

The presence of the amino acid gamma-carboxyglutamate (GLA) was established in human middle ear bones. Proteins containing GLA have been described as being associated with normal as well as pathological calcifications. The GLA content of human incus, malleus, and stapes with 1-2 nmol/mg bone is in the range previously reported for a variety of bone. A limited number of samples with middle ear pathology, including otosclerosis, did not show altered GLA levels.