Helfman P M, Bada J L
Proc Natl Acad Sci U S A. 1975 Aug;72(8):2891-4. doi: 10.1073/pnas.72.8.2891.
The aspartic acid in human tooth enamel shows increasing racemization with age. This increase is not seen in the metabolically active protein hemoglobin. The rate constant for the racemization reaction of aspartic acid in human tooth enamel was found to be 8.29 X 10(-4) yr-1. This rate constant suggests that in any protein with a long in vivo lifetime, D-aspartic acid will accumulate with age (about 8% of total aspartic acid in enamel will be the D-enantiomer after 60 years). Thus, racemization may play some role in the aging process affecting metabolically stable tissues in long-lived homeotherms. Aspartic acid racemization in toogh enamel also provides a biochronological tool for assessing the age of living mammals.
人类牙釉质中的天冬氨酸随着年龄增长呈现出越来越多的消旋化现象。这种增加在代谢活跃的蛋白质血红蛋白中并未出现。人类牙釉质中天冬氨酸消旋化反应的速率常数为8.29×10⁻⁴年⁻¹。该速率常数表明,在任何体内寿命较长的蛋白质中,D - 天冬氨酸会随着年龄积累(60年后,牙釉质中总天冬氨酸的约8%将是D - 对映体)。因此,消旋化可能在影响长寿恒温动物代谢稳定组织的衰老过程中发挥一定作用。牙釉质中的天冬氨酸消旋化也为评估现存哺乳动物的年龄提供了一种生物年代学工具。