Investigation of the α‐Galactosidase Deficiency in Fabry's Disease Using Antibodies against the Purified Enzyme

1. α‐Galactosidase A, the enzyme deficient in Fabry's disease, was purified from normal human urine. The final preparation hydrolysed about 50 μmol p ‐nitrophenyl‐α‐galactoside per h per mg protein at 37 °C. An antiserum against this enzyme was raised in rabbits. Preincubation of preparations of normal kidney and urine with the antiserum, followed by centrifugation, led to a marked reduction of the α‐galactosidase activity of the preparations. 2. There was no influence of the antiserum on the residual α‐galactosidase activity in Fabry kidney or urine, or on an α‐galactosidase B preparation from normal urine. 3. Pretreatment of the antiserum with urine or kidney preparations from a Fabry patient did not result in detectable loss of antibodies reacting with α‐galactosidase A, as shown by the unimpaired ability of the antiserum to diminish α‐galactosidase activity in normal kidney and urine. Furthermore, double immunodiffusion of the pretreated antiserum with a partially purified α‐galactosidase preparation, showed that antibodies not absorbable by the Fabry material were still present in the antiserum. 4. Incubation of normal urinary α‐galactosidase with antiserum, followed by centrifugation and enzyme assay in the supernatant, led to the same reduction of α‐galactosidase activity, regardless of whether a Fabry urine or kidney preparation was simultaneously present or not. 5. It is concluded that no detectable cross‐reacting material was present in this case of Fabry's disease.