5 주 Gycoysis 5.1 Gycoysis의일반적특징 Gycoysis - Gucose가 degradation 과정을거쳐두개의 pyruvate를형성하는과정. - 이때발생하는 free energy는 ATP와 NADH로보존됨. - Gucose 2 Pyruvate - ADP phosphoryation을통하여, ATP 형성 - NAD + 로 hydride ion 전달 (reduction) 하여 NADH 형성 Fate of pyruvate - Gycoysis 과정에의해생성된 pyruvate는산소의유무에따라, 다른과정을거침 - 산소가충분히존재할경우 : citric acid cyce을거쳐 H 2 O와 CO 2 로분해됨. 이과정에서전자를 NAD + 와 FAD로전달하여, 미토콘드리아의전자전달계를거쳐다수의 ATP를합성할수있음. - 산소가부족할경우 : Fermentation을통하여, acoho이나 actate를형성함. Fermentation - Anaerobic condition 에서의 gucose degradation 과정 ATP 생성 Gycoysis 반응식 Gucose + 2NAD + + 2ADP + 2Pi 2pyruvate + 2NADH + 2ATP + 2H + +2H 2 O Gycoysis 과정을통하여 2개의 ATP를합성하지만, gucose에포함되어있던대부분의에너지는 pyruvate에저장됨. - Energy in pyruvate Gucose CO 2 + H 2 O Gucose + 2NAD + 2pyruvate + 2NADH + 2H + 5.2 Gycoysis 단계 1) 1 단계 : Gucose Gucose 6-phosphate
Hexokinase에의하여진행되는반응. - Soube, cytosoic protein - Hexose의인산화에작용함. Hexokinase의기질은 gucose, fructose, mannose 등을포함함. - Mg 2+ 이 cofactor로작용함. 즉, ATP 4- 가아닌 MgATP 2- 가 substrate임. 2) 2 단계 : Gucose 6-phosphate Fructose 6-phosphate Phosphohexose isomerase 에의한반응. 3) 3 단계 : Fructose 6-phosphate Fructose 1,6-bisphosphate Phosphofructokinase-1 에의한반응. - Gycoysis 과정중주된조절포인트임. 4) 4단계 : Fructose 1,6-bisphosphate Dihydroxyacetone phosphate + Gyceradehyde 3-phosphate Adoase에의한반응 - Vertebrate anima에서는 Divaent cation이필요하지않음. - Microorganism에서는 Zn 2+ 이필요한경우가있음. Mechanism은 Schiff base 형성과분해과정을거침 5) 5 단계 : Dyhydroxyacetone phosphate Gyceradehyde 3-phosphate Triose phosphate isomerase 에의한반응 6) 6단계 : Gyceradehyde 3-phosphate 1,3-Bisphosphogycerate Gyceradehyde 3-phosphate dehydrogenase에의한반응 - NAD + 의 reduction이이루어지는단계로서, energy conservation step임. 7) 7단계 : 1,3-Bisphosphogycerate 3-phosphogycerate Phosphogycerate kinase에의한반응 - 효소의명칭은역반응에대한명칭임. 8) 8 단계 : 3-Phosphogycerate 2-phosphogycerate Phosphogycerate mutase 에의한반응
- Mutase 는 intramoecuar functiona group transfer 에관여하는효소로서, isomerase 의일종. 9) 9 단계 : 2-Phosphogycerate Phosphoenopyruvate Enoase 에의한반응 10) 10단계 : Phosphoenopyruvate pyruvate Pyruvate kinase - K + 와 Mg 2+ 이요구됨. - 비가역적인반응임. - 중요 reguation step Eno form Keto form : Tautomerization 5.3 Gycoysis 전체반응의특징 Overa reaction Gucose + 2NAD + + 2ADP + 2Pi 2pyruvate + 2NADH + 2ATP + 2H + +2H 2 O Channeing - Gycoysis에관여하는효소들은복합체를형성하고있음. 연속적인빠른효소반응이가능함. 5.4 Gycoysis의조절 ATP의생산 - Anaerobic condition에서는 2ATP/gucose 생산 - Aerobic condtion에서는 32ATP/gucose 생산 - Pasteur effect: 일정수준의 ATP를유지하기위해 anaerobic condtion 에서 gucose consumption속도가더빠름 Aosteric reguation을받는중요효소들 - Phosphofructokinase-1 - Pyruvate kinase
5.5 Feeder pathways for gycoysis Phosphoroysis - Gycogen, starch gucose - Gycogen phosphoryase - Cofactor: Pyridoxa phosphate Poysaccharides의소화 / 흡수를통한공급 - 입안에서침속에있는 α-amyase에의해분해가시작이됨. Gycosidic bond를끊음. oigosaccharide 형성. - 위에서, α-amyase의불활성화가이루어짐. - 소장에서 pancreatic α-amyase에의해지속적인분해가이루어져서, matose, dextrin을형성함. - Matose와 dextrin은 intestina brush border에서분해됨 - 소장상피세포에서흡수됨. Fructose의 gycoysis 1) Fructose + ATP fructose 6-phosphate + ADP - Hexokinase에의한반응. - Fructose가 gycoysis로들어가는 main pathway. 2) Fructose +ATP fructose 1-phosphate +ADP - fructokinase에의한반응 - 간에서 fructose가 gycoysis로들어가는 pathway. - Fructose 1-phosphate는 Fructose 1-phosphate adoase에의해 gyceradehyde와 dihydroxyacetone phosphate로분해 5.6 Guconeogenesis Formation of new sugar : Gucose 의공급이불충분할겨우 Lactate Pyruvate Amino acids Gucose Gycero
Gycoysis 의 3 개의 exergonic reaction irreversibe: gycoysis 와 guconeogenesis 에서다른 enzyme 들이관여 NADH의공급 : Two paths from pyruvate to PEP - Guconeogenesis는 NADH 필요 - Cytoso에는 reducing agent (NADH 등 ) 의비율이미토콘드리아보다낮음 - Cytoso [NADH]/[NAD + ] = 8 10-4 (About 10 5 times ower than in mitochondria) - Pyruvate에서출발 : Reducing equivaent인 maate의형태로 cytoso로이동 NADH 공급 - Lactate에서출발 : Lactate dehydrogenase가 NADH 공급. Pyruvate의형태로 cytoso로이동