Presentation on theme: "Pentose Phosphate CH339K. Pentose Phosphate An example of a pathway that can be both: Anabolic –Generates ribose-5-phosphate for nucleotide synthesis."— Presentation transcript:
Pentose Phosphate An example of a pathway that can be both: Anabolic –Generates ribose-5-phosphate for nucleotide synthesis –Metabolizes dietary pentoses into glycolytic/gluconeogenic intermediates. Catabolic –Generates reducing power (NADPH) –Can completely oxidize glucose –Can carry on into glycolysis Aka Hexose Monophosphate Shunt
NADH vs NADPH As a general rule of thumb: NAD + /NADH is used in catabolic processes NADP + /NADPH is used in anabolic processes
Glutathione -SH containing tripeptide Glu-Cys-Gly Amino of Cysteine linked to -carboxyl of glutamate Commonly used for reducing agent in cells Oxidizes to for disulfide-linked GSSG Rereduced to GSH using NADPH
Making Glutathione For the Reaction to form GSH: GSSG + 2e - + 2H + ⇄ 2GSH-0.23 V NADPH + H + ⇄ NADP + + 2e - + 2 H + +0.32 V GSSG + NADPH + H + ⇄ 2GSH + NADP + +0.09 V We can figure out G o from what we learned about redox reactions
Divicine is found in fava beans and some other legumes Favas (broad beans) are common foodstuffs in the old world. Largest production in Europe and China. The parent plant, Vicia faba, is among the oldest cultivated plants - ~6,000 years. For what it’s worth…
Glucose-6-P Dehydrogenase Deficiency Effects ~ 4*10 8 people worldwide Most common human genetic disease Lack of G-6PD means lack of NADPH Lack of NADPH means lack of GSH Lack of GSH means excess of peroxides RBC membranes particularly susceptible to peroxides Hemolytic Anemia
Transaldolase moves 3-carbon units Lack of transketolase can cause hepatosplenomegaly and liver cirrhosis in childhood. Verhoeven, N. M. et al (2001) Transaldolase Deficiency: Liver Cirrhosis Associated with a New Inborn Error in the Pentose Phosphate Pathway, Amer. J. Hum. Gen. 68(5): 1086-1092.
Control Conversion of glucose-6-Pi to the lactone is essentially irreversible. The enzyme, glucose-6-phosphate dehydrogenase, controls the rate of the pathway. –NADPH competes with NADP for binding in he active site; –ATP competes with glucose-6-phosphate. At high [NADPH] and/or high [ATP], entrance into the pathway is restricted.