Pentose Phosphate Pathway Flashcards
purpose of PPP?
produce NADPH, Ribose-5-P, provide entry point for pentose sugars in diet
why is NADPH important?
it is the source of biosynthetic reducing power for f.a., steroids, etc.
why is rib-5-P important?
it is needed to synth nucleotides
what is the first phase of PPP?
oxidative generation of NADPH from Gluc-6-P; 3 reactions (6th C becomes CO2)
what is the second phase of PPP?
nonoxidative interconversion of various sugars; 3 reactions
where does PPP take place?
adrenal glands for steroid synth; liver for f.a. and cholesterol synth; testes and ovaries for steroid synth; adipose for f.a.;
In the oxidative phase, are the three reactions reversible?
No, they are irreversible
In the nonoxidative phase and the intermediate reactions, are these 5 reactions reversible?
Yes
what is the name of the enzyme for the redox reaction in the first step of oxidative phase?
glucose 6-P dehydrogenase
what is the name of the enzyme for the ring-opening reaction in oxidative phase?
lactonase
what is the name of the enzyme for the second redox reaction that causes the 6C sugar to become a 5C sugar?
6-Phosphogluconate dehydrogenase
what reaction does phosphopentose isomerase catalyze?
conversion of ketose sugar to aldose sugar–>the 4th reaction
what reaction does phosphopentose epimerase catalyze?
ribulose 5-P –> xylulose 5-P (differ at C3)–>the 5th reaction
what enzyme converts the 5-C sugars into a 3C and 7C sugar?
transketolase (transfers keto group to carbon in ribose-5-P)–>moves 2-C units
what is the prosthetic group for transketolase?
TPP
