title: Is erythrocyte alkaline phosphatase activity a marker of zinc status in humans?
abstract: The identification of an enzyme activity that responds to changes in Zn intake may serve as a useful biomarker for Zn status. Alkaline phosphatase (ALP) is a dimeric protein with each subunit containing two Zn atoms. The activity of ALP in erythrocytes (E) decreases as a result of a low Zn diet, which suggests that this enzyme may be a marker of Zn status. To investigate this further, we determined the response of E-ALP in six healthy subjects following supplementation with 50 mg Zn (4.2 x RDI) daily for 4 wk. A small but significant increase in plasma Zn was observed with supplementation (p < 0.05), whereas there was no significant change in E-Zn over the same period. Plasma and E-Cu showed no change. Conversely, the activity of E-ALP increased in all subjects from 1.7 +/- 0.5 to 5.9 +/- 0.7 U/g protein (mean +/- SE) (p < 0.0001). The small change observed in plasma Zn is not biologically significant in view of the many documented factors that influence its concentration. Our data support the hypothesis that E-ALP is a marker of Zn status in humans.
authors.affiliation: Department of Biochemistry, University of Sydney, NSW, Australia.
authors.forename: S
authors.initials: S
authors.lastname: Samman
authors.forename: C
authors.initials: C
authors.lastname: Soto
authors.forename: L
authors.initials: L
authors.lastname: Cooke
authors.forename: Z
authors.initials: Z
authors.lastname: Ahmad
authors.forename: E
authors.initials: E
authors.lastname: Farmakalidis
mesh_terms: D000328:Adult; D000469:Alkaline Phosphatase / Q000097:blood*; D001315:Australia; D015415:Biomarkers / Q000097:blood; D003300:Copper / Q000097:blood; D004305:Dose-Response Relationship, Drug; D004912:Erythrocytes / Q000187:drug effects / Q000201:enzymology*; D006801:Humans; D008297:Male; D013334:Students; D015032:Zinc / Q000008:administration & dosage / Q000097:blood* / Q000494:pharmacology
chemical_list: D015415:Biomarkers; D003300:Copper; D000469:Alkaline Phosphatase; D015032:Zinc