《生物化学Biochemistry》双语课件 06 维生素Vitamin and Coenzyme.pptVIP

2007-12-27 维生素B1缺乏,糖代谢受阻,丙酮酸积累 血、尿、脑组织丙酮酸含量增多，出现多发性神经炎，皮肤麻木，心力衰竭，肌肉萎缩。下肢浮肿等 脚气病 Lipoate Two thiol groups ----- reversible oxidation to a disulfide bond (-S-S-) hydrogen bonds between chains in the triple helix : amide protons--- carbonyl oxygens, the OH groups of hydroxyproline －stabilizing the structure. hydroxylysine residues －attachment sites for polysaccharides Lipoic acid in amide linkage with a Lys residue electron hydrogen carrier acyl carrier 10. Vitamin C (Ascorbic Acid) ? a water-soluble enzyme acidic acts as a potent antioxidant, protecting against damage by reactive oxygen species (2,3 site --- OH) L- ascorbic Acid dehydro-ascorbate 2 Antioxidants such as vitamin A, vitamin C, and vitamin E provide protection against oxidative damage from reactive oxygen species, such as superoxides, hydroxyl radicals, hydrogen peroxide. a role in making cross links between amino acids in collagen胶原蛋白 Vitamin C Collagen fibers---- form the matrix, or cement, material in bone, on which the mineral constituents precipitate. an important constituent of tendons and skin Collagen : widespread modification proline to hydroxyproline lysine to hydroxylysine The hydroxylation羟基化作用 reactions in collagen involve vitamin C 羟化酶维持活性所必需的辅因子 prolyl 4-hydroxylase reaction 1000 residues in length 3-fold helical left-hand helices 3.3 residues/turn right-hand sense, with hydrogen bonds extending between the chains. Gly–X–Y X and Y are generally Pro or 4-Hyp scurvy 坏血病------vitamin C deficiency the weakening of collagen fibers caused by the failure to hydroxylate proline and lysine. Consequences : Lesions develop in skin and gums, and blood vessels weaken. Why Sailors, Explorers, and College Students Should Eat Their Fresh Fruits and Vegetables Louis IX’s army end of the Seventh Crusade (1248–1254) Scurvy! estimated that a million sailors died of scurvy in the years 1600 to 1800. L-Ascorbic acid (vitamin C) --- white, dorless,c