Citrate binding of Al3+ and Fe3+.
Citrate occurs at about 0.1 mM in blood plasma and is the most likely small molecule plasma binder of both Al3+ and Fe3+. This paper assesses published stability constants for citrate binding to each metal ion. From pH 2 to 5 Al3+ forms a neutral complex with citrate that may be absorbed into the body in the upper regions of the gastrointestinal tract. It is especially dangerous to ingest aluminum-containing antacids with citrus fruit or juices. Ignoring the likely occurrence of a competing 2:1 citrate-Fe3+ complex necessitates adjustments in reported stability constants for Fe3+ binding to transferrin. In the blood, plasma transferrin steals both Fe3+ and Al3+ from citrate.
D000535:Aluminum / Q000097:blood; D002951:Citrates / Q000097:blood; D006801:Humans; D007501:Iron / Q000097:blood; D007700:Kinetics; D014168:Transferrin / Q000378:metabolism
D002951:Citrates; D014168:Transferrin; D000535:Aluminum; D007501:Iron