Question

1. When the cell’s ATP supply is depleted, which of the following enzyme’s activity is increased?

1. Hexokinase
2. Pyruvate kinase
3. Glucokinase
4. Phosphofructokinase

Explain why this enzyme activity is tied to ATP levels.

2. The pyruvate kinase catalyzed step is not a reversible reaction in glycolysis, how then does gluconeogenesis start from pyruvate? Show the mechanism of the first step of gluconeogenesis.

3. Which of the following cofactors do not form a covalent bond with enzymes' lysine residues?

1. Lipoamide
2. Biotin
3. NADH
4. Pyridoxyl phosphate
5. All of the above
6. None of the above

4. Choose any one of the cofactors in question 3 and show an enzymatic mechanism that uses the co-factor with complete arrow pushing. Please draw the entire cofactor structure in your answer at least once. Show the mechanism.

5. Which of the following is NOT true for the reaction catalyzed by the PDC (pyruvate dehydrogenase complex)?

1. The reaction occurs in the mitochondrial matrix
2. The substrate is held by the lipoamide-lysine ‘swinging arm’
3. Two different cofactors that contain the thiol group participate in the reaction
4. Biotin is used for the decarboxylation step.

Answer 1

3) cofactors which do not form covalent bond with lysine-

B- biotin, C- NADH

5) D- biotin is used for the decarboxylation step

The detailed mechanisms and other answers are attached in the following images-

SEPTEMBER 2011 Monday Week 38 1) When the cell's ATP supply is depleted, the following enzyme's activity is increased ;- 6) Pyruvate kinase. Pyruvate kinase is responsible for catalyzing the transfer of phosphate from phosphoenopyruvate (PEP to ADP to form ATP and pyruvate. 2) During gluconeogenesis, Pyruvate is carboxylized to oxalo acetate by Pyruvate carboxylate (Pc). The oxaloacetate produced is converted into phosphoenol pyruvate and co by Phosphoenol pyruvate carboxykinase (PCK) We only admit our little faults to persuade others that we have no great ones.

Tucsudy ZU (2) Pyruvate Week 38 (2) HCO3 + (ATP 3 Pynewate carboxylase (2) ADP (2) Oraloacetate 2GT1 PEP carboxykin 6)CO2 + 2GDPR (2) PEP (2) 3-phosphoglycerate (2)ATP (2) ADP phosphoglycerate kinase E (2) 1,3- Bisphosphoglycerate NADHH I NADT Fructose-1,6-Bisphosphate fi Fructose-1-6-bisphosphatase fructose-6-phosphate Glucose-6-phosphate P. Gucose-6-phosphatase Glucose M T W T F S S M T W T F S S 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

Thursday Week 38 3 Colactors which form covalent bond with Denzyme's lysine residues : - a) topamide - Forms bond with lysine SCHL I CH₂ Lipoic acid NH and S-cr. "CH₂ - CH2 - Chy-CH ₂ -C-NH (CH) - CH Lipoamide. - Lysine c=0 -o-p=0 doxal phosphate (PLP) - Forms bond with lysiue CH2 NI Stru OH CH3 soolio CHZ SEPTEMBER M T W T F S S MTWTFSS 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25