Isolation of an inhibitor of 25-hydroxyvitamin D3-1-hydroxylase from rat serum

Abstract

An inhibitor of chick kidney mitochondrial 25-hydroxyvitamin D3-1-hydroxylase was isolated from rat serum by ammonium sulfate precipitation, gel filtration, ion-exchange chromatography and preparative polyacrylamide disc gel electrophoresis. The purified protein contains Fe and has a MW of 52,000. The protein is indistinguishable on gel electrophoresis from a similar inhibitor found in rat kidney tissue. The physiological significance of the inhibitor is not known; however, it may be responsible for the failure to demonstrate in vitro 25-hydroxyvitamin D3-1-hydroxylation with rat and other mammalian tissues.