Menatetrenone, also known as MK-4, is a vitamin K compound used as a hemostatic agent, and also as adjunctive therapy for the pain of osteoporosis. Menatetrenone is one of the nine forms of vitamin K2 and is a short-chain menaquinone. MK-4 is produced via conversion of vitamin K1 in the body, in the testes, pancreas and arterial walls (Wikipedia). Vitamin K2 is found in brassicas. Vitamin K2 is widely distributed in green leaves and vegetables. It is a fat-soluble dietary factor effective in controlling blood coagulation. All members of the vitamin K group of vitamins share a methylated naphthoquinone ring structure and vary in the aliphatic side chain attached at the 3-position. Phylloquinone (also known as vitamin K1) invariably contains in its side chain four isoprenoid residues, one of which is unsaturated. Human milk contains between 1 and 4 micrograms/litre of vitamin K1, while formula-derived milk can contain up to 100 micrograms/litre in supplemented formulas. Vitamin K2 concentrations in human milk appear to be much lower than those of vitamin K1. It is estimated that there is a 0.25 to 1.7 percent occurrence of vitamin K deficiency bleeding in the first week of the infant's life with a prevalence of 2-10 cases per 100,000 births. The biochemistry of how vitamin K is used to convert glutamic acid (Glu) to gamma-carboxyglutamic acid (Gla) has been elucidated over the past thirty years in academic laboratories throughout the world. Within the cell, vitamin K undergoes electron reduction to a reduced form of vitamin K (called vitamin K hydroquinone) by the enzyme vitamin K epoxide reductase (or VKOR). Another enzyme then oxidizes vitamin K hydroquinone to allow carboxylation of Glu to Gla; this enzyme is called the gamma-glutamyl carboxylase or the vitamin K-dependent carboxylase. The carboxylation reaction will only proceed 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 reactions. Vitamin K epoxide is then re-converted into vitamin K by the vitamin K epoxide reductase. These two enzymes comprise the so-called vitamin K cycle. Vitamin K2 is one of the reasons why vitamin K is rarely deficient in a human diet (vitamin K is continually recycled in our cells). Vitamin K1 is also known as phylloquinone or phytomenadione (also called phytonadione). Vitamin K2 (menaquinone, menatetrenone) is normally produced by bacteria in the large intestine, and dietary deficiency is extremely rare unless the intestines are heavily damaged or are unable to absorb the molecule, or due to decreased production by normal flora, as seen in broad spectrum antibiotic use.