B6 3 pp - Vitamin B6 Spring 2011 Spring 2011 Pages 264-269...

Info iconThis preview shows pages 1–8. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Vitamin B6 Spring 2011 Spring 2011 Pages 264-269 Vitamin B 6 : History • First identified rats: 1930’s –antidermatitis, antianemia factor • Deficiency & convulsive seizures infants 1950’s Heat Treated Experimental Human Infant B6 Deficiency • Experimental B6 deficiency infants – deprived of B6 in formula for purpose of documenting clinical symptoms and response to therapy. • Unethical human experimentation. • Parents of infants not fully informed. Experimental B6 Deficiency Infants Deprived of B6 B6 • Structurally-related compounds •Pyridoxine: alcohol (PN) Vitamin B 6 : Chemistry •Pyridoxal: aldehyde (PL) •Pyridoxamine: amine (PM) •5’-phosphate derivatives of above Fig. 9-35, p. 364 Vitamin B6 Stability • Light sensitive • Heat sensitive –particularly pyridoxal-P Vitamin B6 Stability –pyridoxine-HCL more stable •used in foods that are heat processed –pasteurized infant formulas –major form in supplements and fortified foods Vitamin B6 Food Sources • Best-M eat (0.3 mg / 3 oz) • white-meat chicken, turkey, fish •Fruits & vegetables (~0.8 mg/serving) • nuts • beans • banana • Fortified products • ready-to-eat cereal Vitamin B 6 : Absorption • Small intestine • Passive diffusion, nonsaturable • Alkaline phosphatase dephosphorylates PLP dephosphorylates PLP – free vitamin enters enterocyte • rephosphorylated with ATP and pyridoxal kinase inside cell • Bioavailability – Mixed diet: 75% – Supplement: >90% Transport •Transport: albumin –mainly PLP mainly PLP –Pyridoxal phosphate (PLP) •Coenzyme form Vitamin B 6 : Metabolism •Pyridoxine oxidase required to convert other forms to PLP –FAD dependent enzyme Fig. 9-36, p. 364 Vitamin B 6 : Storage & Excretion • Body store: 60-170 mg – 80-90% in muscle – Bound to phosphorylase – Overall body half life: ~25 days Vitamin B 6 Excretion • Urinary excretion –4-pyridoxic acid •primary excretory product •reflects recent dietary intake –may not reflect long-term status >100 reactions: coenzyme PLP • Types of reactions PLP dependen Vitamin B 6 : Functions dependent –Amino acid metabolism •transamination •deamination –Hormone & neurotransmittor •decarboxylation Transamination • Catabolism of nearly all amino acids involves –transfer of their amino groups to - keto acids. • Major amino group acceptors are – -ketoglutarate and pyruvate • Transamination initally –generate the keto acid of the Transamination amino acid and PMP • Reversal of reaction using - ketoglutarate and pyruvate – generates glutamate or alanine Transamination α-ENZ • PLP first forms a Schiff base with enzyme and then with amino acid – a conjugated double bond system...
View Full Document

{[ snackBarMessage ]}

Page1 / 21

B6 3 pp - Vitamin B6 Spring 2011 Spring 2011 Pages 264-269...

This preview shows document pages 1 - 8. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online