Lysyl oxidase (LOX), a cuproprotein, was assayed for functional activity using a method adapted from Trackman et al. (Anal. Biochern. 113:336, 1982) using cadaverIne and tropoelastin as substrates. In chicks, tendon LOX activity was linearly correlated (r2 = >0.9) with dietary Cu over a wide range of intakes (0 to 16 ug Cu per g diet). Serum Cu levels in these chicks ranged from 0. H to 0.21 nmol Cu per ml, consistent with the concept that LOX activity is regulated, in part, by Cu availability. In related studies, we determined that LOX activity in developing rat embryos (gestation day (GD) 9 to 20) correlated with the net production of extracellular matrix proteins, e.g. collagen. The highest values for activity per g of tissue were observed at GD 13-14 (corresponding to 30-60 ug LOX per g of embryo). In RT-PCR assays, LOX mRNA was easily detected at this period. Previously, we demonstrated that the linear increase in LOX activity in response to dietary Cu is not related to changes in LOX protein or steady-state LOX mRNA levels (J Nutr. 126:51, 1996). Rather, the relationship may be explained by observations that LOX secretion and Cu egress from connective tissue cells can share a common pathway (FASEB J 10:A293, 1995). It is hypothesized that Cu at the active site of LOX facilitates the formation of lysyl-tyrosylquinone as a post-translational event (cf. Science 273:1079, 1996). Methods are in development to measure lysyl-tyrosylquinone to assess its relationship to LOX activity and tissue Cu levels.
|Original language||English (US)|
|State||Published - 1997|
ASJC Scopus subject areas
- Agricultural and Biological Sciences (miscellaneous)
- Biochemistry, Genetics and Molecular Biology(all)
- Cell Biology