Biotin 6 pp - BIOTIN Spring 11 Reading Assignment 342-348...

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Unformatted text preview: BIOTIN Spring 11 Reading Assignment 342-348 Biotin Deficiency Raw egg white diet – Egg yolk cured “egg white injury” • Avidin in raw egg whites • Binds to avidin • Resistant to pancreatic enzymes – Dermatitis, hair loss, neurological abnormalities Fig. 9-19, p. 343 Biotin: Structure Fig. 9-20, p. 343 Biotin: Food Sources • Richest sources – Egg yolk – Peanut butter • Intestinal microflora Biotin: Absorption • Dietary biotin is mainly protein- bound Biotinidase in secretions of • Biotinidase in secretions of pancreatic secretions –hydrolysis of biotin-protein • Active transport- carrier mediated uptake Biotin: Absorption –Sodium-dependent multivitamin transporter (SMVT) • transports lipoic acid & pantothenic acid • Passive diffusion: large doses Absorption of Bacterially Synthesized (colon) Biotin • Bacteria synthesize biotin in colon. Unknown how much is absorbed • Unknown how much is absorbed • Studies have shown colonic epithelial cells capable of absorbing biotin Biotin: Transport • ~80% free • Protein-bound –albumin – -globulin –biotinidase Transport of Biotin into Liver • Sodium dependent multivitamin transporter (SMVT) transports biotin into liver cells biotin into liver cells Biotin Excretion • Urinary excretion • Intact biotin ~50% of excreted • Biotin catabolites Fig. 9-26, p. 347 Table 9-2, p. 344 Fig. 9-21, p. 344 • Biotin-dependent carboxylases – catalyze the incorporation of bicarbonate into a substrate as a Biotin: Function bicarbonate into a substrate as a carboxyl group Fig. 9-22, p. 345 Attachment of the biotin to the apocarboxylase Catalyzed by holocarboxylase synthetase Biotin: Functions • Acetyl CoA carboxylase • Catalyze the incorporation of bicarbonate into acetyl Co A to form malonyl CoA Acetyl CoA Carboxylase Aceytl CoA + HCO + ATP → ← Malonyl CoA ↓ Fatty Acid Synthesis Complex Practice Question A patient with severe biotin deficiency has abnormal fatty acid synthesis. Select the correct name of the enzyme(s) for which biotin functions as a coenzyme in the fatty acid biosynthesis pathway acid biosynthesis pathway. (a) acetyl CoA carboxylase (b) pyruvate carboxylase (c) methyl malonyl CoA mutase (d) -methyl crotonyl CoA carboxlase (e) all of the above Practice Question A patient with severe biotin deficiency has abnormal fatty acid synthesis. Select the correct name of the enzyme(s) for which biotin functions as a coenzyme in the fatty...
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This note was uploaded on 12/09/2011 for the course HUN 4445 taught by Professor Sitren during the Spring '08 term at University of Florida.

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Biotin 6 pp - BIOTIN Spring 11 Reading Assignment 342-348...

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