Gaucher disease: a membranous enzymopathy.

Area of Science:

• Biochemistry
• Enzymology
• Molecular Biology

Background:

• Acid beta-glucosidase is a membrane-bound enzyme crucial for cellular processes.
• Type 1 Ashkenazi Gaucher disease is a membranous enzymopathy linked to acid beta-glucosidase deficiency.
• Understanding the enzyme's active site is key to elucidating disease mechanisms.

Purpose of the Study:

• To characterize the active site components of membrane-bound acid beta-glucosidase using inhibitors and activators.
• To investigate alterations in the hydrophobic site of acid beta-glucosidase in Type 1 Ashkenazi Gaucher disease patients.
• To hypothesize the molecular basis of Gaucher disease related to enzyme mutations.

Main Methods:

• Utilized inhibitors and activators as probes to study acid beta-glucosidase activity.
• Analyzed kinetic data from residual enzyme in Gaucher disease homozygotes.
• Proposed potential molecular mechanisms, including single base substitutions affecting amino acid composition or enzyme conformation.

Main Results:

• Defined three active site components: catalytic, aglycon binding, and hydrophobic binding sites.
• Suggested the hydrophobic site in Gaucher disease patients is more hydrophilic than normal.
• Hypothesized that this alteration leads to reduced substrate turnover (Vmax mutation) and less efficient binding of certain molecules.

Conclusions:

• A mutation altering the hydrophobic site's hydrophilicity could explain the defect in Type 1 Ashkenazi Gaucher disease.
• Such mutations may not affect substrate binding affinity (Km) but reduce catalytic efficiency (Vmax).
• Further confirmation requires amino acid sequencing of purified enzyme from normal and Gaucher disease sources.