| Autor: |
Houben RJ; Department of Biochemistry and Cardiovascular Research Institute, Maastricht University, P.O. Box 616, 6200 MD Maastricht, The Netherlands., Rijkers DT, Stanley TB, Acher F, Azerad R, Käkönen SM, Vermeer C, Soute BA |
| Jazyk: |
angličtina |
| Zdroj: |
The Biochemical journal [Biochem J] 2002 May 15; Vol. 364 (Pt 1), pp. 323-8. |
| DOI: |
10.1042/bj3640323 |
| Abstrakt: |
Two different sites on vitamin K-dependent gamma-glutamyl carboxylase (VKC) are involved in enzyme-substrate interaction: the propeptide-binding site required for high-affinity substrate binding and the active site for glutamate carboxylation. Synthetic descarboxy osteocalcin (d-OC) is a low-K(m) substrate for the VKC, but unique since it possesses a high-affinity recognition site for the VKC, distinct from the propeptide which is essential as a binding site for VKC. However, the exact location and composition of this VKC-recognition domain on d-OC has remained unclear until now. Using a stereospecific substrate analogue [t-butyloxycarbonyl-(2S,4S)-4-methylglutamic acid-Glu-Val (S-MeTPT)] we demonstrate in this paper that the high affinity of d-OC for VKC cannot be explained by a direct interaction with either the active site or with the propeptide-binding site on VKC. It is shown using various synthetic peptides derived from d-OC that there are two domains on d-OC necessary for recognition: one located between residues 1 and 12 and a second between residues 26 and 39, i.e. at the C-terminal side of the gamma-carboxyglutamate (Gla) domain. Both internal sequences contribute substantially to the efficiency of carboxylation. On the basis of these data we postulate the presence of a second high-affinity substrate-binding site on VKC capable of specifically binding d-OC, which is the first vitamin K-dependent substrate of which the VKC binding domain is interrupted by the Gla domain. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
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