Comparison of purine and MTA phosphorylases. The beginning of MTA phosphorylases is aligned with that of purine phosphorylases extracted from phylogenetically widely diverse organisms: PSEAE Pseudomonas aeruginosa; THETE Thermoanaerobacter tengcongensis; HOMSA Homo sapiens; CAEEL Caenorhabditis elegans; SCHPO Schizosaccharomyces pombe; SYNEC Synechocystis PCC 6803; MYCTU Mycobacterium tuberculosis; METJA Methanococcus jannaschii; METTH Methanobacterium thermoautotrophicum; LEPIN Leptospira interrogans; XYLFA Xylella fastidiosa; ESCHO Escherichia coli; SACCE Saccharomyces cerevisiae; BACSU Bacillus subtilis; GEOST Geobacillus stearothermophilus; BOSTA Bos taurus. Conserved residues in both classes of enzymes are emphasized . In red are shown conserved residues that are specific to one class, while conservative replacements are indicated in blue. The three residues in green indicate a region that suffered an insertion/deletion event in the course of evolution that separated the two classes. The position of the first residue of the alignment shown is displayed in blue. Note that for Synechocystis the published sequence starts earlier, but that the residue indicated is likely to be the real start of the protein.