Cohen-Solal L, Lian J B, Kossiva D, Glimcher M J
Biochem J. 1979 Jan 1;177(1):81-98. doi: 10.1042/bj1770081.
Non-collagenous phosphoproteins, almost all of which can be extracted in EDTA at neutral pH in the presence of proteinase inhibitors, are identified in the matrix of chicken bone, and are therefore not covalently bound to collagen. Similarly, all the peptides containing gamma-carboxyglutamic acid are present in the EDTA extract and none in the insoluble residue, confirming that none is covalently linked to chicken bone collagen. However, organic phosphorus is also found to be present in chicken bone collagen, principally in the alpha2-chains. Of the total protein-bound organic phosphorus present in chicken bone matrix, approx. 80% is associated with the non-collagenous proteins and 20% with collagen. The soluble non-collagenous proteins contain both O-phosphoserine and O-phosphothreonine and these account for essentially of their organic phosphorus content. In contrast, collagen contains neither O-phosphoserine nor O-phosphothreonine. Indeed, no phosphorylated hydroxy amino acid, phosphoamidated amino acid or phosphorylated sugar could be identified in purified components of collagen, which contain approximately four to five atoms of organic phosphorus per molecule of collagen. Peptides containing organic phosphorus were isolated from partial acid hydrolysates and enzymic digests of purified collagen components, which contain an as-yet-unidentified cationic amino acid. These data, the very high concentrations of glutamic acid in the phosphorylated peptides, and the pH-stability of the organic phosphorus moiety in intact collagen chains strongly suggest that at least part of the organic phosphorus in collagen is present as phosphorylated glutamic acid. This would indicate that the two major chemically different protein fractions in chicken bone matrix that contain organic phosphorus may represent two distinct metabolic pools of organic phosphorus under separate biological control.
在鸡骨基质中鉴定出了非胶原蛋白磷蛋白，几乎所有这些蛋白在中性pH值下、存在蛋白酶抑制剂的情况下都能在乙二胺四乙酸（EDTA）中提取出来，因此它们并非与胶原蛋白共价结合。同样，所有含γ-羧基谷氨酸的肽都存在于EDTA提取物中，而不溶性残渣中则没有，这证实了没有任何一种肽与鸡骨胶原蛋白共价相连。然而，也发现鸡骨胶原蛋白中存在有机磷，主要存在于α2链中。在鸡骨基质中存在的与蛋白质结合的总有机磷中，约80%与非胶原蛋白相关，20%与胶原蛋白相关。可溶性非胶原蛋白同时含有O-磷酸丝氨酸和O-磷酸苏氨酸，这些基本上构成了它们的有机磷含量。相比之下，胶原蛋白既不含有O-磷酸丝氨酸也不含有O-磷酸苏氨酸。实际上，在纯化的胶原蛋白成分中未鉴定出磷酸化的羟基氨基酸、磷酰胺化氨基酸或磷酸化糖，每分子胶原蛋白中大约含有4至5个有机磷原子。从纯化的胶原蛋白成分的部分酸水解物和酶消化物中分离出了含有有机磷的肽，这些肽含有一种尚未鉴定的阳离子氨基酸。这些数据、磷酸化肽中谷氨酸的极高浓度以及完整胶原蛋白链中有机磷部分的pH稳定性强烈表明，胶原蛋白中的至少部分有机磷以磷酸化谷氨酸的形式存在。这表明鸡骨基质中含有有机磷的两种主要化学性质不同的蛋白质组分可能代表在不同生物控制下的两个不同的有机磷代谢库。
