Harden-Young ester

Fructose 1,6-b/sphosphate,/rucrose 1,6-diphosphate, Harden-Young ester, a derivative of fructose in which the OH groups of Cl and C6 are esterified with phosphoric acid. It is an important intermediate of Glycolysis (see). 

Harden-Young ester see lactose 1,6-bfrphos-phate. 

A number of hexose phosphates have been isolated from natural sources. Of these oTructose 1,6-diphosphate (Harden-Young ester) (I), D-fructose 6-phosphate (Neuberg ester) (II), D-glucose 6-phosphate (Robison ester) (III), and a-D-glucose 1-phosphate (IV) are of particular biochemical importance in the processes of fermentation and glycolysis. These hexose phosphates are interconvertible in the presence of the proper enzymes and cofactors. 

Hexose Diphosphate.— Fructofuranose-1 6-diphosphoric acid, (Harden-Young ester), CsHjo04(HgP04)2, is formed in the first stage of the fermentation of glucose, mannose or fructose by yeast. The phosphate on hydrolysis by boiling yields fructose, and its formation is an example of the interconvertibility of the three monosaccharides. It is also an early product in the conversion of glycogen into lactic acid, in muscle. 

Two phosphate esters, fructose 6-phosphate and fructose 1,6-diphosphate (the Harden-Young ester) are biochemically significant because they are intermediates in the breakdown of glucose according to the Embden-Meyerhof pathway (Section 7) this pathway is actually the route of breakdown of fructose 1,6-diphosphate. 

It has long been known that fermentation by yeast extracts normally comprises at least three phases an initial induction period followed, within a matter of about five or ten minutes, by a very rapid fermentation this persists for some time and passes over into a prolonged relatively slow action. All this has been measured by carbon dioxide production. This is true not only for glucose, shown, e.g., by Meyerhof (53,54), but also for galactose (40) and for fructose (34). These have been attributed to the formation of the hexose-6-phosphate (Robison ester) which must precede any carbon dioxide liberation, and the conversion of this to hexose-1,6-diphosphate (Harden-Young ester), which ferments slowly. The maximum of hexose-6-phosphate concentration coincides with the maximum car-... 

Fructose-1,6-diphosphate Harden and Young ester)—Fructofura-nose-1, 6-diphosphate in alkaline solution (0 2N NaOH) at 100° liberates the whole of its phosphate in three minutes. 

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