Abstract | BACKGROUND: The determination of cellular beta- galactocerebrosidase activity is an established procedure to diagnose Krabbe disease and monitor the efficacy of gene/stem cell-based therapeutic approaches aimed at restoring defective enzymatic activity in patients or disease models. Current biochemical assays for beta- galactocerebrosidase show high specificity but generally require large protein amounts from scanty sources such as hematopoietic or neural stem cells. We developed a novel assay based on the hypothesis that specific measurements of beta- galactocerebrosidase activity can be performed following complete inhibition of beta-galactosidase activity. METHODS: We performed the assay using 2-7.5 microg of sample proteins with the artificial fluorogenic substrate 4-methylumbelliferone-beta-galactopyranoside (1.5 mmol/L) resuspended in 0.1/0.2 mol/L citrate/ phosphate buffer, pH 4.0, and AgNO(3). Reactions were incubated for 30 min at 37 degrees C. Fluorescence of liberated 4-methylumbelliferone was measured on a spectrofluorometer (lambda(ex) 360 nm, lambda(em) 446 nm). RESULTS: AgNO(3) was a competitive inhibitor of beta-galactosidase [inhibition constant (K(i)) = 0.12 micromol/L] and completely inhibited beta-galactosidase activity when used at a concentration of 11 micromol/L. Under this condition, the beta- galactocerebrosidase activity was preserved and could be specifically and accurately measured. The assay can detect beta- galactocerebrosidase activity in as little as 2 microg cell protein extract or 7.5 microg tissue. Assay validation was performed using (a) brain tissues from wild-type and twitcher mice and (b) murine GALC(-/-) hematopoietic stem cells and neural precursor cells transduced by GALC-lentiviral vectors. CONCLUSIONS: The procedure is straightforward, rapid, and reproducible. Within a clinical context, our method unequivocally discriminated cells from healthy subjects and Krabbe patients and is therefore suitable for diagnostic applications.
|
Authors | Sabata Martino, Roberto Tiribuzi, Andrea Tortori, Daniele Conti, Ilaria Visigalli, Annalisa Lattanzi, Alessandra Biffi, Angela Gritti, Aldo Orlacchio |
Journal | Clinical chemistry
(Clin Chem)
Vol. 55
Issue 3
Pg. 541-8
(Mar 2009)
ISSN: 1530-8561 [Electronic] England |
PMID | 19147730
(Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
|
Chemical References |
- Silver Nitrate
- beta-Galactosidase
- Galactosylceramidase
|
Topics |
- Animals
- Cells, Cultured
- Chromatography, Gel
- Enzyme Activation
(drug effects)
- Galactosylceramidase
(analysis, metabolism)
- Humans
- Mice
- Mice, Inbred C57BL
- Silver Nitrate
(pharmacology)
- Tissue Culture Techniques
- beta-Galactosidase
(antagonists & inhibitors, metabolism)
|