Physiological Functions And Pharmacologicalactions

Phylloquinone and menaquinones are virtually devoid of pharmacodynamic activity. However, in subjects deficient in vitamin K, the vitamin performs its normal physiological function: to promote the biosynthesis of the g-carboxy-glutamate (Gla) forms of factors II (prothrombin), VII, IX, and X, anticoagulant proteins C and S, protein Z (a cofactor to the inhibitor of Xa), the bone Gla protein osteocalcin, matrix Gla protein, and growth arrest-specific protein 6 (Gas6). Figure 54-6 summarizes the coupling of the vitamin K cycle with glutamate carboxylation. Vitamin K, as KH2, the reduced hydroquinone, is an essential cofactor for g-glutamyl carboxylase. Using KH2, O2, CO2, and the glutamate-containing substrate, the enzyme forms a g-carboxy-glutamatyl protein (Gla protein) and concomitantly, the 2,3-epoxide of vitamin K. A coumarin-sensitive 2,3-epoxide reductase regenerates KH2. The g-glutamyl carboxylase and epoxide reductase are integral membrane proteins of the endoplasmic reticulum and function as a multicomponent complex. Two natural mutations in g-glutamyl carboxylase lead to bleeding disorders. With respect to proteins affecting blood coagulation, these reactions occur in the liver, but g-carboxylation of Glu also occurs in lung, bone, and other cell types.

Diabetes 2

Diabetes 2

Diabetes is a disease that affects the way your body uses food. Normally, your body converts sugars, starches and other foods into a form of sugar called glucose. Your body uses glucose for fuel. The cells receive the glucose through the bloodstream. They then use insulin a hormone made by the pancreas to absorb the glucose, convert it into energy, and either use it or store it for later use. Learn more...

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