GRT1 Task 4 Enzymology and catalytic mechanism

Significant amounts of fructose, which is formed by cleaving a sucrose before entering the portal vein system, converted to glucose in the gut cells. Another part of the fructose is absorbed via transfer protein, i.e. lightweight by diffusion. Figure 1. Metabolism of fructose Metabolism of fructose (Figure 1) starts with the phosphorylation reaction catalyzed by fructokinase with the formation of fructose-1-phosphate. The enzyme is found in liver and kidney and intestine. This enzyme has an absolute specificity, however, unlike glucokinase, insulin does not affect its activity. The latter circumstance explains why the level of excretion of fructose in the urine of patients with diabetes and healthy is no different. Fructose-1-phosphate can be converted to fructose-6-phosphate because of the lack of appropriate enzyme. Instead of fructose-1-phosphate is cleaved more fructo-1-fosfataldolazoy (aldolase B) dihydroxyacetone and glyceraldehyde-3-phosphate. The latter is the intermediate of glycolysis and is formed in the reaction catalyzed by fructose-1,6-bisfosfosfataldolazoy (aldolase A). Glyceraldehyde may be included in glycolysis after phosphorylation with ATP. Or two triose phosphate molecules decompose on the glycolytic pathway, or condensed to form fructose 1,6-bisphosphate and more involved in gluconeogenesis. Fructose in the liver mainly included in the second path. Part dihydroxyacetone-3-phosphate can be reduced to glycerol-3-phosphate and participate in the synthesis of triacylglycerols. It should be noted that the inclusion of fructose metabolism by fructose-1-phosphate bypasses step catalyzed by phosphofructokinase, which is the point of metabolic control of glucose catabolism rate. This fact may explain why the increase in the amount of fructose in the liver accelerate processes leading to the synthesis of fatty acids and their esterification to form triacylglycerols.arusheniya fructose metabolism. Lack fructokinase not clinically manifested. Fructose accumulates in the blood and is excreted in the urine where it can be detected by laboratory methods. It is important not to confuse this harmless abnormality with diabetes. This condition is known as benign essential fructosuria and occurs at a frequency of 1: 130 000.Hereditary fructose intolerance, occurs when genetically determined defect of fructose-1-fosfataldolazy, does not appear until the child is fed breast milk, ie while the food does not contain fructose. Symptoms occur when added to the diet of fruit juices, sucrose. Vomiting, abdominal pain, diarrhea, hypoglycemia, and even coma and convulsions occur within 30 minutes after a meal containing fructose. In young children and adolescents continue to take fructose develop chronic disorders of the liver and kidneys. Fructose intolerance - quite common autosomal recessive form of pathology. Defect aldolase fructose-1-phosphate is accompanied by accumulation of fructose-1-phosphate, which inhibits fosfoglyuko-mutase, converts glucose-1-phosphate to glucose 6-phosphate and including providing a reaction product glikogenfosforilaznoy metab...

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