Galactosidase, urate oxidase and laronidase

Human a-galactosidase is a 100 kDa homodimeric glycoprotein. Each 398 amino acid monomer displays a molecular mass of 45.3 kDa (excluding the glycocomponent) and is glycosylated at three positions (asparagines 108, 161 and 184). After administration (usually every second week by a 40 min infusion), the enzyme is taken up by various body cell types and directed to the lysosomes. This cellular uptake and delivery process appear to be mediated by mannose- 

6-phosphate residues present in the oligosaccharide side-chains of the enzyme. Mannose-6-phos-phate receptors are found on the surfaces of various cell types, and also intracellularly, associated with the golgi complex, which then directs the enzyme to the lysosomes. 

The enzyme urate oxidase has also found medical application for the treatment of acute hype-ruricaemia (elevated plasma uric acid levels), associated with various tumours, particularly during their treatment with chemotherapy. 

CH12 RECOMBINANT BLOOD PRODUCTS AND THERAPEUTIC ENZYMES 

Purine metabolism in some mammals is characterized by a further oxidation of uric acid to al-lantoin by the enzyme urate oxidase. Allantoin is significantly more water soluble than uric acid and is also freely excreted via the renal route. 

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