SEMINARS!!!! Dr. Christopher M. Reddy, Woods Hole Oceanographic Institution. Jean Dreyfus Boissevain Lectureship "Hunting for Subsurface Oil Plumes in the Gulf of Mexico Following the Deepwater Horizon Disaster" Jean Dreyfus Boissevain Lectureship Location: SL150 Reception: 3:15 pm; Lecture: 4:00 pm Webpage Webpage

Exam R 6-8 pm Sl 140

Figure 21-6The five reactions of the PDC. Pyruvate + CoA + NAD + →Acetyl CoA + CO 2 + NADH Page 770 Nucleophile and electron sink

Advantages of Multienzyme Complexes 1. Proximity→rate enhancements 2. Channeling—passing substrates around 3. Coordinated Control

Figure 21-6The five reactions of the PDC. Pyruvate + CoA + NAD + →Acetyl CoA + CO 2 + NADH Page 770 Nucleophile and electron sink

Advantages of Multienzyme Complexes 1. Proximity→rate enhancements 2. Channeling—passing substrates around 3. Coordinated Control

Figure 21-17aFactors controlling the activity of the PDC. (a) Product inhibition. Page 781

Figure Factors controlling the activity of the PDC. (b) Covalent modification in the eukaryotic complex. Page 781

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The succinyl-CoA synthetase reaction. (b) Active site of succinyl-CoA synthetase of E. coli. The active site includes part of both the α and the β (brown) subunits. The power helices place the partial positive charges of the helix dipole near the phosphate group of P– His246 in the α chain, stabilizing the phosphohistidyl enzyme.

COO - CH 3 - +CoASH  CH 3 C=O CoASH When in the TCA cycle would this label be lost as CO 2 ?

Figure Regulation of the citric acid cycle. Page 791

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The role of biotin in the reaction catalyzed by pyruvate carboxylase. Biotin is attached to the enzyme through an amide bond with the ε-amino group of a Lys residue, forming biotinyl-enzyme. Biotin-mediated carboxylation reactions occur in two phases, generally catalyzed in separate active sites on the enzyme as exemplified by the pyruvate carboxylase reaction.

The role of biotin in the reaction catalyzed by pyruvate carboxylase. Biotin- mediated carboxylation reactions occur in two phases, generally catalyzed in separate active sites on the enzyme as exemplified by the pyruvate carboxylase reaction. In the first phase (steps 1 to 3), bicarbonate is converted to the more activated CO 2, and then used to carboxylate biotin.

The biotin acts as a carrier to transport the CO 2 from one active site to another on an adjacent monomer of the tetrameric enzyme.

In the second phase (steps 5 to 7), catalyzed in this second active site, the CO2 reacts with pyruvate to form oxaloacetate.

“Alfonse, Biochemistry makes my head hurt!!” \