METABOLIC BIOCHEMISTRY Summer 2005 Lecture 6 August 12, 2005

LNC Chapter 16 The Citric Acid Cycle Krebs Cycle TCA Cycle

From G. Perkins, C. Renken, M.E. Martone, S.J. Young, M. Ellisman, and T. Frey

Outer membrane Inner membrane Intermembrane space Matrix

Pyruvate dehydrogenase as seen by electronmicroscopy E. coli enzyme: Mass > 4.5x copies of trans acetylase (E2) 24 copies of pyruvate dehydrogenase (E1) 12 copies of dihydro- lipoyl dehydrogenase Pyruvate + CoASH + NAD +  acetyl-CoA + CO 2 + NADH

E1E1 E3E3 E2E2

LNC 16.3 Coenzyme A

LNC Lipoamide

LNC Fig FAD/FMN FADH 2 /FMNH 2

Fig. 16.6

Figure from previous edition of LNC

TCA CYCLE Krebs cycle Citric acid cycle

LNC Products from one turn of the Krebs cycle C4 C6 C2 C5 C4 C6

LNC 16.8 Citrate Synthase open form without substrates closed from with substrates bound oxaloacetate: yellow acetyl-coA: red

LNC 16.9 Iron-sulfur center in aconitase

X

Stereospecificity of the aconitase reaction with citrate

LNC 16.14

LNC Fig.16.7 the only membrane- bound enzyme in the TCA cycle

LNC Fig regulatory molecules: NADH ATP, ADP Ca +2 key allosteric enzymes: the dehydrogenases citrate synthase

LNC Fig the Krebs cycle is amphibolic

THE GLYOXYLATE CYCLE LNC Chapter 16, pages

LNC Fig Note that the figure in the 3 rd edition has an error (there is an O instead of an H) C6C6 C6C6 C4C4 C4C4 C4C4 C2C2 C2C2 C2C2 from oxidation of fatty acids

LNC Fig.16.22

End of lecture 6 August 12, 2005