Vitamin K-dependent γ-glutamylcarboxylase in Atlantic salmon (Salmo salar L.)
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Due to problems with bone deformities in farmed Atlantic salmon, there is a growing interest in the possible involvement of vitamin K in normal bone development, and sensitive biomarkers for evaluating vitamin K status are therefore needed. The vitamin K-dependent (VKD) enzyme γ-glutamylcarboxylase (GGCX, EC 6.4.x.x) requires vitamin K as a cofactor for its post-translational modification of glutamic acid (Glu) residues to γ-carboxyglutamic acid (Gla) residues in VKD proteins, and is required for their function in haemostasis and bone metabolism. The present study was designed to evaluate the enzyme assay for GGCX activity in isolated liver microsomes and its distribution in the tissues of Atlantic salmon. The effect of KH2 and menadione on the GGCX activity in salmon liver was also compared. Results from the present study show a widespread tissue distribution and expression of GGCX in Atlantic salmon. The GGCX activity and ggcx expression in all bony tissues examined imply the presence of vitamin K, and suggest the involvement of vitamin K in bone metabolism of Atlantic salmon. We propose the GGCX assay as a sensitive marker for vitamin K status, and confirm that menadione does not work as a cofactor for GGCX in Atlantic salmon liver.
KeywordsVitamin K Enzyme assay Atlantic salmon Tissue distribution Cofactor γ-Glutamylcarboxylase
This project is part of a research program called Roles of Fat Soluble Vitamins in Bone Development and Mineral Metabolism, funded by The Research Council of Norway (project # 153472). The authors would like to thank Dr. Rune Waagbø for constructive comments to the manuscript.
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