γ-Glutamyl Transpeptidase in Brain Capillaries: Possible Site of a Blood-Brain Barrier for Amino Acids

Abstract

A fraction containing capillaries and rich in gamma-glutamyl transpeptidase was isolated from homogenates of bovine brain cortex by density gradient centrifugation. The enzyme was localized in the endothelial cells by a histochemical procedure. gamma-Glutantyl transpeptidase may function in the transfer of some amino acids across the blood-brain barrier.