the gut organ contains bacteria that help produce vitamin k.
the gut organ contains bacteria that help produce vitamin k.
what organ contains bacteria that help produce vitamin k?
gut
the mk-4 form of vitamin k is produced by conversion of vitamin k in the testes, pancreas, and arterial walls. while major questions still surround the biochemical pathway for this transformation, the conversion is not dependent on gut bacteria, as it occurs in germ-free rats and in parenterally administered k in rats. in fact, tissues that accumulate high amounts of mk-4 have a remarkable capacity to convert up to 90% of the available k into mk-4. there is evidence that the conversion proceeds by removal of the phytyl tail of k to produce menadione as an intermediate, which is then condensed with an activated geranylgeranyl moiety (see also prenylation) to produce vitamin k in the mk-4 (menatetrenone) form.
vitamin k
within the cell, vitamin k undergoes electron reduction to a reduced form called vitamin k hydroquinone, catalyzed by the enzyme vitamin k epoxide reductase (vkor). another enzyme then oxidizes vitamin k hydroquinone to allow carboxylation of glu to gla; this enzyme is called gamma-glutamyl carboxylase or the vitamin k-dependent carboxylase. the carboxylation reaction only proceeds if the carboxylase enzyme is able to oxidize vitamin k hydroquinone to vitamin k epoxide at the same time. the carboxylation and epoxidation reactions are said to be coupled. vitamin k epoxide is then reconverted to vitamin k by vkor. the reduction and subsequent reoxidation of vitamin k coupled with carboxylation of glu is called the vitamin k cycle. humans are rarely deficient in vitamin k because, in part, vitamin k is continuously recycled in cells.
vitamin k