Hauschka P V, Reid M L
J Biol Chem. 1978 Dec 25;253(24):9063-8.
Bone contains a small protein, osteocalcin, rich in the amino acid gamma-carboxyglutamate (gammaCGlu), which is dependent on vitamin K for its synthesis. The vitamin K dependence of osteocalcin biosynthesis has been studied both in the developing chicken embryo and in the skeletons of young chicks. Osteocalcin formation, assessed by quantitation of gammaCGlu in whole bone, begins in the 8-day embryonic skeleton and increases dramatically until hatching. Biosynthesis of gammaCGlu is warfarinsensitive; time- and dose-related inhibition of up to 75% is observed. Vitamin K deficiency reduces bone gammaCGlu concentrations by 50% in 3-week-old chicks, and this is totally corrected by including vitamin K1 in the diet. Feeding the vitamin K antagonist dicumarol decreases the bone gammaCGlu level 80% after 6 weeks, but no corresponding alterations are observed in the calcium and phosphorous content of the bone ash. Osteocalcin purified from bones of dicumoral-fed chicks exhibits several electrophoretically variant undercarboxylated protein species containing 2 and 3 gammaCGlu/57 amino acid residues rather than the normal complement of 4 gammaCGlu/57 residues.
骨骼中含有一种小蛋白质——骨钙素，富含氨基酸γ-羧基谷氨酸（γCGlu），其合成依赖维生素K。骨钙素生物合成对维生素K的依赖性已在发育中的鸡胚胎和幼雏骨骼中进行了研究。通过定量全骨中的γCGlu来评估骨钙素的形成，始于8日龄胚胎骨骼，并在孵化前急剧增加。γCGlu的生物合成对华法林敏感；观察到高达75%的时间和剂量相关抑制。维生素K缺乏会使3周龄雏鸡骨骼中的γCGlu浓度降低50%，而在饮食中添加维生素K1可完全纠正这一情况。喂食维生素K拮抗剂双香豆素6周后，骨骼γCGlu水平降低80%，但骨灰中的钙和磷含量未观察到相应变化。从喂食双香豆素的雏鸡骨骼中纯化的骨钙素在电泳中表现出几种变体，即含有2个和3个γCGlu/57个氨基酸残基的羧化不足蛋白质物种，而非正常的4个γCGlu/57个残基。
