ConA-mediated binding and uptake of purified alpha-galactosidase A in Fabry fibroblasts

In most human tissues there are at least two different alpha-galactosidases, A and B. The former is deficient in patients hemizygous for Fabry disease. We have isolated it from human placenta and found that it was labile even at culture conditions, but was stabilized after binding to concanavalin A (conA). The alpha-galactosidase activity was markedly increased in Fabry fibroblasts when these were treated with conA and exposed to alpha-galA at 37 degrees C. The maximum activity was obtained after 1/2-2 h of incubation and was maintained for at least 4 h. The binding and uptake of conA into Fabry cells was followed by microscopical studies of fluorescein-labelled conA. We assume that alpha-galA is taken up by endocytosis of the enzyme-conA complex.