title: Genetic polymorphism of glutamate-pyruvate transaminase (alanine aminotransaminase): influence on erythrocyte activity as a marker of vitamin B-6 nutritional status.
abstract: A new, sensitive, two-step method free from interference by hemoglobin that measures erythrocyte glutamate-pyruvate transaminase (E-GPT) activity is described. Several aspects of E-GPT activity as an index of vitamin B-6 nutritional status were investigated with this method. 1) GPT shows a structural genetic polymorphism with two common alleles resulting in three phenotypes. In a population study (n = 92) E-GPT activity differed significantly (p less than 0.001) among the three phenotypic groups. Plasma pyridoxal-5'-phosphate concentrations in the three groups did not differ significantly. Therefore, E-GPT activity can only be used to assess vitamin B-6 nutritional status if GPT phenotype is accounted for. 2) Pyridoxine supplementation (10 mg/d) significantly (p less than 0.0001) increased E-GPT activity and decreased (p less than 0.0001) the percentage stimulation by pyridoxal-5'-phosphate in vitro although the absolute amount of in vitro stimulation by pyridoxal-5'-phosphate changed only marginally. 3) Inorganic phosphate inhibits in vitro activation of E-GPT by pyridoxal-5'-phosphate.
authors.affiliation: Department of Chemical Pathology, University of Pretoria, South Africa.
authors.forename: J B
authors.initials: JB
authors.lastname: Ubbink
authors.forename: S
authors.initials: S
authors.lastname: Bissbort
authors.forename: I
authors.initials: I
authors.lastname: van den Berg
authors.forename: L S
authors.initials: LS
authors.lastname: de Villiers
authors.forename: P J
authors.initials: PJ
authors.lastname: Becker
mesh_terms: D000410:Alanine Transaminase / Q000097:blood / Q000235:genetics*; D004912:Erythrocytes / Q000187:drug effects / Q000201:enzymology*; D006801:Humans; D009752:Nutritional Status; D010641:Phenotype; D010710:Phosphates / Q000494:pharmacology; D011110:Polymorphism, Genetic; D011732:Pyridoxal Phosphate / Q000097:blood / Q000494:pharmacology; D011736:Pyridoxine / Q000008:administration & dosage / Q000494:pharmacology
chemical_list: D010710:Phosphates; D011732:Pyridoxal Phosphate; D000410:Alanine Transaminase; D011736:Pyridoxine