Sialidases amino acid sequence

In no case is the amino acid composition of a sialidase yet known, and complete insight into the amino acids involved in enzyme catalysis is unavailable. There is one report demonstrating a possible involvement of tryptophan residues in enzyme catalysis.331 Establishing of the complete, amino acid sequence of sialidases from different sub-types of influenza virus is to be expected from the determination of the nucleotide sequence of the viral genome by using a plasmid technique.332 Preliminary results revealed the identity of the first 12 amino... 

In the first primary structures of microbial sialidases, obtained by cloning and sequencing of the respective genes from Clostridium perfringens [769], Vibrio cholerae [770], Clostridium sordellii [77 ] and Salmonella typhimurium [772], an amino acid sequence motif was detected, which is repeated four-fold in each protein S-X-D-X-G-X-T-W [773]. This motif, named the Asp-box, was found in all 16 sialidases of animals, trypanosomes, and bacteria, which have so far been sequenced (see refs. [660,768] and Table 18). In viral sialidases, however, the motif was rarely detectable (e.g. only the sialidase from N9 influenza A virus strain exhibits the complete motif [786] and has probably undergone mutational alterations). 

X. Amino Acid Sequence Variants in Human Sialidases... 

Recently, a cDNA clone encoding the cytosolic sialidase of rat skeletal muscle was prepared and expressed in Escherichia coli (Miyagi et al., 1993). The nucleotide sequence encodes 379 amino acid residues with a calculated molecular mass of 42,381 Da. The deduced amino acid sequence does not resemble any of the viral, bacterial, or parasitic sialidases, although it contains two Asp blocks, which are conserved in these enzymes (Roggentin et al., 1989). 

Two trans-sialidases isolated from the animal-pathogenic Afiican trypanosome T. Congo lense show pronounced differences in their capacity for sialic acid transfer as compared with the hydrolytic activity. Partial sequences were obtained from these two enzymes by a PCR-based approach, showing 50% identity with each oflier, but are similar to viral, bacterial, animal siahdases and other trans-sialidases. Most of the critical active-site residues common to other trypanosomal siahdases and TS are conserved This similarity, together with the amino acid difference at the active site, between American and African (trans-)siahdases is depicted in the pubUcation. ... 

Antigenic determinants were found across the top surface of the sialidase monomer and encircling the active site [62], Of importance for inhibitor development, the active site was seen to contain a large number of amino acids that were conserved in all influenza A and B virus sialidase sequences known to that time [34,62]. This suggested that the active site residues were under pressure to remain constant [69], and that this was an invariant area of the sialidase that could be targeted for inhibitor development against the otherwise highly mutable [4] protein. 

---