NUTR 3330 Lecture Notes - Lecture 3: Mitogen, Glycogen Phosphorylase, Hemoglobin
20 Sep 2017
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Dermatitis: avidin binds to biotin very tightly, once biotin-avidin complex forms, it is irreversible, not broken down, excreted in feces, prevents absorption, avidin can be denatured by cooking affinity for biotin is therefore destroyed. Holocarboxylase synthase deficiency: holocarboxylase synthase attaches biotin to lysine residue of carboxylase enzymes, children with holocarboxylase synthase deficiency often have immunodeficiency diseases, proposes to play a role in sids single carboxylase deficiency. Biochemical results of biotin deficiency: decrease in biotin-dependent enzymes, decrease pyruvate carboxylase. Less glucose produced: decreased acetyl coa carboxylase. Urinary metabolites; diagnostic: accumulation of biotin substrates. B-methylcrotonate (enzyme for biotin leucine metabolism) B-hydroxypropionate: sometimes lactase as well (relates to pyruvate carboxylase) Food sources (biotin: not much data available from food composition tables, liver, whole-grain cereals, nut, legumes, peanut butter, low in fruits and vegetables. Bacterial synthesis: biotin can also be synthesized by intestinal bacteria urine and fecal amounts > dietary amounts, amount absorbed is unknown, implications for long-term anti-biotic use.
