Effects of ultraviolet light on free and peptide-bound pyridinoline and deoxypyridinoline cross-links. Protective effect of acid pH against photolytic degradation
B. Meddah et al., Effects of ultraviolet light on free and peptide-bound pyridinoline and deoxypyridinoline cross-links. Protective effect of acid pH against photolytic degradation, J PHOTOCH B, 54(2-3), 2000, pp. 168-174
Citations number
28
Categorie Soggetti
Biochemistry & Biophysics
Journal title
JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY
Little is known about the photodegradation of pyridinoline (Pyd) and deoxyp
yridinoline (Dpd) which are two mature cross-links stabilizing collagen wit
hin extracellular matrix. In this study, highly purified free Pyd and Dpd c
ross-links have been degraded by irradiation with ultraviolet light and we
have shown that photolysis varies with the FH value. Assessment of photolys
is in basic (pH 9) and neutral (pH 7) solutions by high-performance liquid
chromatography as well as by UV absorbance measurement indicates that both
cross-links are degraded after a 24 h UV exposure, while in acidic solution
(pH 3) only Dpd is photolysed, suggesting that acid pH provides major prot
ection against Pyd photolysis. Photodegradation products have been studied
by amino-acid and mass spectral analysis. Both methods confirm the lack of
Pyd degradation in acid pH. Furthermore, amino-acid analysis allows us to i
dentify hydroxylysine and lysine as a result of Pyd and Dpd photolysis, res
pectively, indicating that the mechanism of photodegradation involves the c
leavage of the pyridinium ring on each side of the quaternary nitrogen. Fin
ally, we have also studied the photolysis of different molecular species of
type I collagen peptides, obtained by digestion with collagenase of demine
ralized turkey bone. Our results indicate that even when they are part of t
he structure of collagen peptide, Pyd and Dpd can be photolysed. However, w
e have shown that the larger the peptide is, the smaller are the effects of
UV irradiation. (C) 2000 Elsevier Science S.A. All rights reserved.