CHP 26: PENTOSE PHOSPHATE PATHWAY

What’s teh key product of PPP & source of biosynthetic reducing power?

NADPH

DEFINE: 1st phase of PPP

Oxidative generation of NAPDH

DEFINE: 2nd phase of PPP

Nonoxidative interconversion of a variety of sugars

Who initiates the conversion of G6-P → 6phosphoglucono-(delta)-lactone; in the process also reduces NADP+ → NADPH

G6-P dehydrogenase

Who converts 6-Pglu-(delta)-L → 6-phosphogluconate

Lactonase

Who converts 6-PG → ribulose 5-phosphate  + CO2 & generates a 2nd NADPH

6-PG dehydrogenase

Who isomerizes ribulose 5-P → ribose 5-P?

Phosphopentose isomerase

PPP is linked to Glycolysis by which two enzymes?

Transketolase & Transaldolase

DEFINE: Transketolase 

Converts 2 5-C sugars → 3-C & 7-C sugar

Who forms Xylulose 5-P by its epimer ribulose 5-P?

Phosphopentose epimerase

DEFINE: Transaldolase 

6-C + 4-C sugar → 3-C + 7-C sugar

DEFINE: Transketolase

4-C sugar + 5-C sugar → 6-C sugar + 3-C sugar

Low [NADP+] will…

inhibit glucose 6-phosphate dehydrogenase—no carrier to receive electrons to allow reaction to take place

High [NADP+] will…

activate glucose 6-phosphate dehydrogenase