J5 pentose phosphate pathway

1、J5 Pentose phosphate pathway Keywords pentose phosphate pathway 磷酸戊糖途径磷酸戊糖途径 ribose 5-phosphate 核糖核糖 5-磷酸磷酸 glucose 6-phosphate dehydrogenase葡萄糖葡萄糖6-磷酸脱氢酶磷酸脱氢酶 transketolase 转酮酶转酮酶 transaldolase 转醛酶转醛酶 Glucose-6-phosphate dehydrogenase deficiency (G6PD缺乏症）缺乏症）is an X-linked recessive hereditary dise

2、ase. It is characterised by abnormally low levels of G6PD, a metabolic enzyme involved in the pentose phosphate pathway, especially important in red blood cell metabolism. Q5: Why G6PD deficiency can also be called favism (蚕豆蚕豆 病病)? 1 Overview Nicotinamide 烟酰胺烟酰胺 adenine 腺嘌呤腺嘌呤 Nicotinamide adenine

3、dinucleotide (NAD+) 烟酰胺腺嘌呤二核苷酸烟酰胺腺嘌呤二核苷酸 carriers of electrons NADH/NADPH The pentose phosphate pathway takes place in the cytosol. The significance of pentose phosphate pathway: To produce two main products (1) NADPH (2) ribose 5-phosphate. (1) the functions of NADPH: 1) to provide hydrogen for man

4、y anabolic (biosynthetic) reactions. e.g. fatty acids and steroids in tissues: adipose tissue, mammary gland and the adrenal cortex. 2) to provide hydrogen for biotransformation. 3) to maintain glutathion (谷胱甘肽）谷胱甘肽）in reductive state (还原状态）还原状态）. 谷胱甘肽还原酶谷胱甘肽还原酶 GSSG + NADPH + H+ 2 GSH + NADP+ FAD G

5、SH的功能是防止巯基酶（蛋白）被氧化的功能是防止巯基酶（蛋白）被氧化 2GSH+ H2O2 G-S-S-G + 2H2O 谷胱甘肽过氧化物酶谷胱甘肽过氧化物酶 Oxidative stress within cells is controlled primarily by the action of the peptide, glutathione,GSH. (2) the functions of ribose 5-phosphate for the synthesis of 1) RNA, DNA 2) NAD, flavine adenine dinucleotide (FAD) 3)

6、ATP 4) coenzyme A (CoA) 5) other important molecules. 2 Main reactions of the pathway (1) Stage 1-Oxidative reactions that convert glucose 6-phosphate into ribulose 5-phosphate, generating two NADPH molecules. Oxidative reactions dehydrogenate NADP+ NADPH+H+ H2O CO2 G-6-P Xylulose 5-P Ribulose 5-P R

7、ibose 5-P G-6-P dehydrogenase 6-Phosphogluconate 6-phosphogluconate dehydrogenase 6-Phospho gluconolactonase 6-phosphogluco- nolactone Epimerase Isomerase NADP+ NADPH+H+ 6磷酸葡萄糖酸内酯磷酸葡萄糖酸内酯 内酯酶内酯酶 6-磷酸葡萄糖酸磷酸葡萄糖酸 6-磷酸葡萄糖酸磷酸葡萄糖酸 脱氢酶脱氢酶 核酮糖核酮糖 5-磷酸磷酸 G6PD (2) Stage2 - Isomerization of ribulose 5- phospat

8、e to ribose 5-phosphate (核糖核糖 5-磷酸）磷酸） (3) Stage 3 - Linkage of the pentose phosphate pathway to glycolysis via transketolase（转酮酶）转酮酶） and transaldolase（转醛酶）转醛酶）. Non-oxidation reaction Ribose 5-p Xylulose 5-p Xylulose 5-p Fructose 6-p Glyceraldehyde 3-p Fructose 6-p 3 Control of the pathway The first reaction of the pathway, the oxidation of glucose 6-