Molecular cloning and expression of mouse brain sialidase

Sialidase (EC 3.2.1.18) catalyzes the release of sialic acid from sialo-oli gosaccharides, gangliosides, or sialo-glycoproteins, In this investigation, we cloned a novel cDNA for mouse brain sialidase and expressed the cDNA in COS-7 cells. This 1,699 bp cDNA codes for a 41.6 kDa protein consisting of 372 deduced amino acid residues, In COS-7 cells transiently transfected wi th the cDNA, a 250-fold increase was observed in specific activity toward 2 '-(4-methylumbelliferyl)-alpha-D-N-acetylneuraminic acid, Similarity search es of the nonredundant GenBank peptide sequence database by the PSI-BLAST p rogram identified rat, hamster, human, and bacterial sialidases homologous to this mouse brain sialidase, Amino acid sequence identities to rat and ha mster sialidases (84% and 77%, respectively) suggest that this form of sial idase is conserved in rodents, Sequence identities to human and mouse lysos omal sialidases (30% and 28%, respectively) indicate that the mouse brain s ialidase is distinct from the lysosomal enzyme. Mouse brain sialidase has t wo amino acid sequence motifs common to bacterial sialidases: the 'F/YRIP' motif and the 'Asp-box' motif. The 'F/YRIP' motif is present near the N ter minus while two 'Asp-box' motifs are present downstream. (C) 1999 Academic Press.