PENTOSE PHOSPHATE PATHWAY Flashcards
What is the primary function of PPP?
Generates NADPH and ribose from glucose-6-phosphate.
What are the two stages of PPP?
A: Oxidative phase and non-oxidative phase.
Key enzyme in the oxidative phase?
Glucose-6-phosphate dehydrogenase
Substrate for glucose-6-phosphate dehydrogenase?
Glucose-6-phosphate
Product of the oxidative phase?
NADPH
Byproduct of the oxidative phase?
CO2.
Function of the non-oxidative phase?
Interconverts sugars
Key enzyme in the non-oxidative phase?
Ribulose-5-phosphate epimerase.
Generation of glucose from non-carbohydrate sources.
gluconeogenesis
Alternative name for PPP
hexose monophosphate shunt
Why is NADPH important?
Essential for fatty acid synthesis, cholesterol synthesis, and antioxidant defenses.
Implication of altered PPP activity in cancer cells
Increased NADPH production for biosynthesis
How is the polyol pathway implicated in diabetes complications?
Converts glucose to fructose, contributing to diabetic neuropathy and cataract formation.
Product of glucose-6-phosphate dehydrogenase?
6-phosphogluconolactone
Enzyme that converts 6-phosphogluconolactone to 6-phosphogluconate?
6-phosphogluconolactonase
Cofactor for glucose-6-phosphate dehydrogenase?
NADP+.
How is glucose-6-phosphate dehydrogenase regulated?
Feedback inhibition by NADPH.
Catalyzes the conversion of glucose-6-phosphate to 6-phosphogluconolactone
glucose-6-phosphate dehydrogenase
Catalyzes the conversion of 6-phosphogluconate to ribulose-5-phosphate
6-phosphogluconate dehydrogenase
cofactor for 6-phosphogluconate dehydrogenase
NADP+
How is 6-phosphogluconate dehydrogenase regulated?
Feedback inhibition by NADPH
Glucuronic acid is synthesized from glucose via this pathway
Uronic acid pathway
Deficiency in the pathway of uronic acid leads to the condition of
essential pentosuria
Deficiencies in the enzymes of fructose and galactose metabolism lead to metabolic disease such as:
essential fructosuria, hereditary fructose intolerance, galactosemia
Two phases of PPP reactions
Irreversible oxidative phase
Reversible nonoxidative phase
A precursor of proteoglycans & conjugated glucuronides. A product of the Uronic Acid Pathway
Glucuronate
It is needed for the synthesis of Lactose, Glycolipids, Proteoglycans, & Glycoproteins
Galactose
catalyzes the phosphorylation of galactose using ATP as phosphate donor
Galactokinase
Precursor of Amino Sugars (Hexosamines)
Glucose
Major amino sugars are
glucosamine, galactosamine, mannosamine, sialic acid
Principal sialic acid found in human tissues
N-acetylneuraminic acid
Both fructose and sorbitol are found in the lens of the eye and may be involved in the pathogenesis of
Diabetic cataract
responsible for fructose formation from glucose
Sorbitol “polyol” pathway
Enzyme that catalyze the reduction of glucose to sorbitol
Aldose reductase
