Purification of feline lysosomal α-mannosidase, determination of its cDNA sequence and identification of a mutation causing α-mannosidosis in Persian cats

α-Mannosidosis is a lysosomal storage disorder that is caused by the deficiency of lysosomal α-mannosidase. Feline αmannosidosis is a well-characterized animal model used for studying pathological and therapeutic aspects of lysosomal storage disorders. We here report the purification of feline liver lysosomal α-mannosidase and determination of its cDNA sequence. The active enzyme consisted of three polypeptides, with molecular masses of 72, 41 and 12 kDa, joined by non-covalent forces. The cDNA sequence of feline lysosomal α-mannosidase was determined from reverse transcriptase PCR products obtained from skin fibroblast mRNA. The deduced amino acid sequence contained the N-terminal sequences of the 72 and 41 kDa peptides. This indicated that the enzyme is synthesized as a single-chain precursor with a putative signal peptide of 50