sentences:  TPST is about 50-54 kD in size, and has two confirmed isoforms in mammals, TPST-1 and TPST-2, that are 370 and 377 residues in length, respectively.Both are quite similar with an approximately 63% amino acid identity, but show slightly different protein substrate specificities.TPST is a prevalent enzyme, found in many multicellular eukaryotes including mammals, most vertebrates, and a number of invertebrate species as well, including "Drosophila melanogaster".