While menadione plus NADH or menadiol is unable to promote in vitro vitamin K-dependent carboxylation in a solubilized rat liver microsomal incubation system (as does vitamin K1 hydroquinone or vitamin K1 plus NADH), addition of various monoand dithiols with the menadione produces activity. Adducts of menadione and a number of thiols have been prepared in pure form and were found to be able to ...

Vitamin K epoxide can occur as a pair of optical isomers due to the asymmetry of the oxirane ring substituents. The stereoselectivity of vitamin K-epoxide reductase for the oxirane ring configuration was determined by recovery of the partially resolved unreacted substrate following incubations of racemic vitamin K epoxide with rat liver microsomes. The substrate ws enriched for the (--)-enantio...

The formation of vitamin K epoxide and the vitamin K-dependent carboxylation of glutamic acid residues present in synthetic substrates and decarboxyprothrombin are both inhibited by superoxide dismutase. Catalase only inhibits the generation of vitamin K epoxide, suggesting that the carboxylation and epoxidation reactions are not inter-dependent.

The present paper describes a system in vitro that has been developed to mimic vitamin K metabolism and vitamin K function in liver. In this system the two pathways that are known to participate in vitamin K reduction are active and the vitamin K-dependent carboxylase accepts a synthetic pentapeptide as substrate. With this system in vitro the effect of warfarin on both pathways was examined un...

Renal diets for advanced chronic kidney disease (CKD) are structured to achieve a lower protein, phosphate and sodium intake, while supplying adequate energy. The aim of this nutritional intervention is to prevent or correct signs, symptoms and complications of renal insufficiency, delaying the start of dialysis and preserving nutritional status. This paper focuses on three additional aspects o...

Atkins GJ, Welldon KJ, Wijenayaka AR, Bonewald LF, Findlay DM. Vitamin K promotes mineralization, osteoblast-to-osteocyte transition, and an anticatabolic phenotype by -carboxylation-dependent and -independent mechanisms. Am J Physiol Cell Physiol 297: C1358–C1367, 2009. First published August 12, 2009; doi:10.1152/ajpcell.00216.2009.— The vitamin K family members phylloquinone (vitamin K1) and...

We measured the vitamin K status in postmortem human tissues (brain, heart, kidney, liver, lung, pancreas) to see if there is a tissue-specific distribution pattern. Phylloquinone (K1) was recovered in all tissues with relatively high levels in liver, heart and pancreas (medians, 10.6 (4.8), 9.3 (4.2), 28.4 (12.8) pmol(ng)/g wet weight tissue); low levels (< 2 pmol/g) were found in brain, kidne...