Enzyme Cofactors Chapter 16 Amino Acids, Proteins, and Enzymes

2 Function of Coenzymes A coenzyme prepares the active site for catalytic activity.

3 Water-Soluble Vitamins Water-soluble vitamins are soluble in aqueous solutions. cofactors for many enzymes. not stored in the body. Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings

4 Fat-Soluble Vitamins Fat-soluble vitamins are A, D, E, and K. are soluble in lipids, but not in aqueous solutions. are important in vision, bone formation, antioxidants, and blood clotting. are stored in the body. Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings

5 Learning Check Identify each compound as a 1) water-soluble vitamin 2) fat-soluble vitamin. A. Folic acid B. Retinol (Vitamin A) C. Vitamin C D. Vitamin E E. Niacin

6 Solution Identify each compound as a 1) water-soluble vitamin 2) fat-soluble vitamin. A. 1 Folic acid B. 2 Retinol (Vitamin A) C. 1 Vitamin C D. 2 Vitamin E E. 1 Niacin

7 Thiamin (Vitamin B 1 ) Thiamin was the first B vitamin identified. is part of the coenzyme thiamin pyrophosphate (TPP), required in the decarboxylation of  -keto carboxylic acids. deficiency results in beriberi (fatigue, weight loss, and nerve degeneration).

8 Riboflavin (Vitamin B 2 ) Riboflavin is made of the sugar alcohol ribitol and flavin. part of the coenzymes flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN). needed for good vision and healthy skin. N NN N HH 3 C H 3 C CH 2 CHCHCHCH 2 OH OHOHOH O O D-Ribitol

9 Niacin (Vitamin B 3 ) Niacin is part of the coenzyme nicotinamide adenine dinucleotide (NAD + ) involved in oxidation- reduction reactions. deficiency can result in dermatitis, muscle fatigue, and loss of appetite. is found in meats, rice, and whole grains. N C O OH

10 Pantothenic Acid (Vitamin B 5 ) Pantothenic acid is part of coenzyme A needed for energy production as well as glucose and cholesterol synthesis. deficiency can result in fatigue, retarded growth, cramps, and anemia. is found in salmon, meat, eggs, whole grains, and vegetables. HOCH 2 CCHCNCH 2 CH 2 COH O H OHOCH 3 CH 3

11 Cobalamin (Vitamin B 12 ) Cobalamin consists of four pyrrole rings with a Co 2+. is a coenzyme for enzymes that transfer methyl groups and produce red blood cells. deficiency can lead to pernicious anemia and nerve damage.

12 Ascorbic Acid (Vitamin C) Vitamin C is required in collagen synthesis. deficiency can lead to weakened connective tissue, slow-healing wounds, and anemia. is found in blueberries, citrus fruits, tomatoes, broccoli, red and green vegetables. O CHOH CH 2 OH OHHO O

13 Folic Acid (Folate) Folic acid (folate) consists of pyrimidine, p-aminobenzoic acid, and glutamate. forms the coenzyme THF used in the transfer of carbon groups and the synthesis of nucleic acids. deficiency can lead to abnormal red blood cells, anemia, and poor growth.

14 Vitamin A is obtained from meats and beta-carotenes in plants. has beta-carotenes that are converted by liver enzymes to vitamin A (retinol). H 3 CCH 3 CH 3 CH 3 CH 3 CH 3 CH 3 H 3 CCH 3 H 3 C CH 3 CH 3 CH 2 OH H 3 CCH 3 CH 3 Beta-carotene Retinol (vitamin A)

15 Vitamin D Vitamin D (D 3 ) is synthesized in skin exposed to sunlight. regulates the absorption of phosphorus and calcium during bone growth. deficiency can result in weakened bones. sources include cod liver oil, egg yolk, and enriched milk.

16 Vitamin E is an antioxidant in cells. may prevent the oxidation of unsaturated fatty acids. is found in vegetable oils, whole grains, and vegetables. O CH 3 HO H 3 C CH 3 CH 3 CH 3 CH 3 CH 3 CH 3

17 Vitamin K Vitamin K 1 in plants has a saturated side chain. Vitamin K 2 in animals has a long unsaturated side chain. Vitamin K 2 is needed for the synthesis of zymogens for blood clotting. 3 n

18 Learning Check Identify the vitamin associated with each 1) Thiamin (B 1 )2) Vitamin A 3) Vitamin K4) Vitamin D 5) Ascorbic Acid A. Collagen formation B. Beriberi C. Absorption of phosphorus and calcium in bone D. Vision E. Blood clotting

19 Solution Identify the vitamin associated with each 1) Thiamin (B 1 )2) Vitamin A 3) Vitamin K4) Vitamin D 5) Ascorbic Acid A. 5 Collagen formation B. 1 Beriberi C. 4 Absorption of phosphorus and calcium in bone D. 2 Vision E. 3 Blood clotting