Biochemistry

two phosphotrioses. The divergence of the oxidation of carbohydrates - the classic - Krebs citrate and the "pentose"cycle begins at the stage of formation of hexosomonophosphate. If hexosomonophosphate (fructose-6-monophosphoric ether) is subjected to phosphorylation once again and is converted into fructose ­ diphosphate, in this case, the further breakdown of carbohydrates occurs along the usual glycolytic path with the formation of phosphotriosis and pyruvic acid, which "bums" then in citric acid "boiler". If the addition of the second phosphate' particle to the hexose-6- monophosphate ether does not occur, then the glucose monophosphate can be directly oxidized with the elimination of CO 2 and the formation of pentose phosphate. Hence the name has arisen - the direct oxidation of carbohydrates in the pentose cycle (Fig. 11.8). Glucose-6-phosphate under the influence of dehydrogenase undergoes dehydrogenation with the formation of first 6-phosphogluconolactone and then 6- phosphogluconic acid HCOH I HCOH ноін 0 I HCOH I HC — J CHjO-P So I . . . HCOH dehydrogenase -------- HOCH d NADP| + H HCOH I HC — 1 CHiO-P + COOH I HCOH +H2 °» HOCH I HCOH I HCOH CHjO-P Glucose-6-phosphate 6-phosphogluconolactone 6-phosphogluconic acid 6-phosphogluconic acid under the influence of dehydrogenase coenzyme, which is also NADP, is undergoes dehydrogenation and then decarboxylation with the formation of pentose phosphate: ribulose-5-phosphate and one CO 2 molecule. The reaction proceeds as follows: 6-phosphogluconic acid 3-keto-6-phosphogluconic acid Ribuloso-5-phosphate 233