vit K Flashcards
what type of vitamin is vit K
Fat soluble vitamin. Along with D, A and E
whys it called vit K
as its importance in blood clotting so vit K for koagulation
when was vit K discovered and who by
Between 1929 and 1935 Henrik Dam discovered a nutrient that had a vital role in blood clotting.
vit K was originally discovered as what kind of disease
haemorrhagic disease of chickens and cattle due to fat-free feed or dicoumarol presence.
what are the strictures of vit K
Two naturally occurring vitamers
- Phylloquinone (K1) - plants
- Menaquinones (K2) - animal sources & synthesized by intestinal bacteria
Synthetic compounds
- menadione
- menadiol diacetate
These are water soluble and can be metabolized to vit K1
what do synthetic vit K antagonists do
interfere with action of vit K by competing for binding sites at receptors so prevent clotting ability
what are examples of synthetic vit K antagonists and what do each of them do
Dicoumarol – excessive intakes impair blood clotting.
Warfarin – developed for clinical use as anticoagulant.
what are the functions of vit K
mainly for blood clotting and bone health
Involved in blood coagulation/ clotting – involved in cascade of reactions involving production of different proteins.
Role in bone proteins. Preventing osteoporosis
Possible role in cell signalling, brain lipid, regulation of calcium in the kidney. But more research is needed so focus on first 2 roles
Role mediated through action of both K1 and K2 acting as co-factor in conversion of protein bound glutamate residues to gamma carboxyglutamate (Gla) in a diverse group of proteins.
explain what vit K is needed as in blood coagulation
Needed as a Co-factor for the carboxylase enzyme that facilitates the synthesis of the unusual amino acid -carboxyglutamic acid (Gla).
what is Gla needed for formation of
Coagulation proteins (prevent bleeding): factors II (prothrombin), VII, IX & X
Anticoagulants: proteins C & S inhibit clotting process
what contain 4 - 6 Gla residues
Prothrombin and other proteins
what does Gla chelate and then permit the binding of
Gla chelates Ca ions and permits binding of blood clotting proteins to lipid membranes. So absence of Gla would cause impaired coagulation process
what does the coagulation/ clotting cascade do
converts blood from liquid to gel, and leads to fibrin formation
explain the full coagulation/ clotting cascade process
the intrinsic pathway occurs from clotting triggered by atherosclerotic plaque. vit K slowly produces thromboplastin
the extrinsic pathway occurs from clotting triggered by a cut finger. vit K fastly produces thromboplastin
Vit K produces thromboplastin which catalyses conversion of prothrombin to thrombin which converts soluble fibrinogen to insoluble strands or threads of fibrin, which is bound to platelets and hardens so forming clot or plug over wound.
Vit K also needed to give preprothrombin which has ability to bind to calcium ions which is important for clotting
explain how vit K is involved in bone formation
Gla present in bone matrix proteins osteocalcin (OC) & bone matrix Gla protein.
Treatment with warfarin or other anticoagulants in pregnancy has lead to foetal bone abnormalities due to impaired synthesis of OsteoCalcin.
OC thought to be involved in limitation of bone growth.
does vit K increase or decrease bone mineral density in osteoporosis
increase
does vit K increase or decrease fracture rates
decrease
vit K works____with vit_____on _____
synergistically (combined affect is greater than sum of individual affect) with vit D on bone density
