Isolation and characterization of human apatite-inducing aortic proteolipid.

A proteolipid, capable of inducing hydroxyapatite in vitro, can be isolated from human aortic calcified lesions, noncalcified lesions, and nonlesion tissue obtained at autopsy. Analysis of the amino acid composition after acid hydrolysis showed all nucleators to be high in the hydrophobic amino acids glycine and alanine. Estimation of the molecular weight of the nucleator, extracted from calcified lesions, by gel filtration and lipid content showed a minimum molecular weight of 469,000 Da. All nucleators were characterized by the presence of acidic phospholipids which may have a role in the mechanism of calcification.