Lefevre M, Rucker R B
Biochim Biophys Acta. 1983 Mar 30;743(3):338-42. doi: 10.1016/0167-4838(83)90391-6.
We have previously demonstrated that aorta elastin, a highly crosslinked protein, does not undergo turnover that is easily measured in vivo. Therefore, it was hypothesized that when proteolysis of elastin occurs, a positive increase in N-terminal amino acids should result. Such an increase would represent elastin-derived fragments held covalently in situ. A cyanate carbamylation procedure was used to estimate the changes in N-terminal amino acids in aorta elastin. To provide tissue for the studies, Japanese quail (3 weeks old) were fed diets with or without the addition of 1% cholesterol. It was found that, in normal birds, the number of N-terminal amino acid residues increased from two to approximately three residues per 800 total residues (or mole of tropoelastin) throughout sexual development (3 to 8 weeks, post-hatching), with little increase thereafter. In hypercholesterolemic birds, the rate of appearance of new N-terminal residues, particularly glutamine or glutamic acid, appeared enhanced throughout early development, but by sexual maturity the number of N-terminal amino acid residues in aorta elastin from cholesterol-fed birds was similar to that for the control birds. For each of the elastin samples analyzed, approximately one residue of glycine was recovered per 800 total residues. Other amino acids that predominated as N-terminal residues were serine, aspartic and glutamic acids.
我们之前已经证明，主动脉弹性蛋白作为一种高度交联的蛋白质，其更新在体内难以轻易测定。因此，有人提出假设，当弹性蛋白发生蛋白水解时，N端氨基酸应会出现正向增加。这种增加将代表原位共价结合的弹性蛋白衍生片段。采用氰酸盐氨甲酰化程序来估计主动脉弹性蛋白中N端氨基酸的变化。为了提供用于研究的组织，给3周龄的日本鹌鹑喂食添加或不添加1%胆固醇的饲料。结果发现，在正常鸟类中，在整个性发育阶段（孵化后3至8周），每800个总残基（或原弹性蛋白摩尔数）的N端氨基酸残基数量从2个增加到约3个残基，此后几乎不再增加。在高胆固醇血症鸟类中，新的N端残基，特别是谷氨酰胺或谷氨酸的出现率在早期发育过程中似乎有所增加，但到性成熟时，喂食胆固醇的鸟类主动脉弹性蛋白中的N端氨基酸残基数量与对照鸟类相似。对于分析的每个弹性蛋白样品，每800个总残基中大约回收一个甘氨酸残基。作为N端残基占主导的其他氨基酸是丝氨酸、天冬氨酸和谷氨酸。
