CHEM 153C Study Guide - Final Guide: Isomerase, Reactive Oxygen Species, Glyceraldehyde
23 Jun 2016
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Functions: generate nadph for biosynthetic reduction reactions, generate 4- and 5-carbon sugars for amino acid biosynthesis (e4p) and nucleotide synthesis (ribose-5-p). _ppp is amphibolic as it serves both catabolic (degradative) and anabolic (biosynthetic) functions. e. g. catabolic - degradation of ribose following phosphorylation anabolic - use ribulose-5-p for photosynthesis; ribose-5-p for nucleotides; or erythrose-4-p for aromatic amino acid synthesis. _the enzymes of the ppp are present at high levels in adipose tissue because fatty acid synthesis requires large amounts of nadph, thus necessitating a large amount of ppp enzymes for nadph synthesis. Rationale: (i) in order to produce all primary products needed (nadph, e4p, r5p, f6p, ga3p), G6p undergoes oxidation to yield nadph and a 5-carbon sugar [ru5p]. Isomerization and epimerization reactions convert this sugar to ribose-5-p. E4p and r5p from the oxidative path (above) can be converted to fructose-6-p and glyceraldehyde-3-p of the glycolytic pathway.
