Boskey A L, Wians F H, Hauschka P V
Calcif Tissue Int. 1985 Jan;37(1):57-62. doi: 10.1007/BF02557680.
Osteocalcin, the bone gamma-carboxy glutamic acid containing protein, is one of the major noncollagenous proteins both synthesized and localized in bony tissue. Previously, investigators have suggested, based on the in vitro and in vivo properties of this protein, that it may be involved in controlling initiation of mineralization and/or hydroxyapatite (HA) growth. In this study, the in vitro effects of osteocalcin on lipid-induced HA formation, and HA seeded growth were compared. Although osteocalcin inhibited the growth of HA, as indicated by the osteocalcin concentration-dependent decreases in the first order rate constant, kCa, osteocalcin had no effect on lipid-induced calcification, kCa remaining constant at .033 h-1. Binding studies revealed that osteocalcin did not associate with the lipid macromolecules tested (phosphatidyl serine, phosphatidyl inositol, and the Ca-acidic phospholipid-phosphate (Ca-PL-PO4) complexes prepared from these phospholipids) although the protein bound to HA with high affinity. These data suggest that a) osteocalcin is quite distinct from the gamma carboxy glutamic acid containing clotting proteins which have a high affinity for both the acidic phospholipids and for HA, and b) that osteocalcin has little effect on the initial Ca-PL-PO4-dependent formation of HA.
骨钙素，即含γ-羧基谷氨酸的骨蛋白，是在骨组织中合成并定位的主要非胶原蛋白之一。此前，研究人员根据该蛋白的体外和体内特性提出，它可能参与控制矿化的起始和/或羟基磷灰石（HA）的生长。在本研究中，比较了骨钙素对脂质诱导的HA形成和HA接种生长的体外影响。尽管骨钙素抑制了HA的生长，如骨钙素浓度依赖性降低一级速率常数kCa所示，但骨钙素对脂质诱导的钙化没有影响，kCa保持在0.033 h-1不变。结合研究表明，骨钙素不与所测试的脂质大分子（磷脂酰丝氨酸、磷脂酰肌醇以及由这些磷脂制备的钙-酸性磷脂-磷酸（Ca-PL-PO4）复合物）结合，尽管该蛋白与HA具有高亲和力。这些数据表明：a）骨钙素与对酸性磷脂和HA都具有高亲和力的含γ-羧基谷氨酸的凝血蛋白截然不同；b）骨钙素对最初的Ca-PL-PO4依赖性HA形成几乎没有影响。
