what do you mean for cell type? human cell line as suggested from nathaniel or organisms, eg a specific bacteria, fungi or mammalian?
in the second case you can BLAST a known sequence of the enzime inside the specific organism that you would check and see if it found some prote in with high homology and with conserved catalitic residues.
Specify the enzyme and search the databases for a broader source, say mammalian cells/ line, insect cell line, murine cell line, primate cell line or human cell line(s). If you have already purified a particular enzyme, resolve it on SDS-PAGE and query the protein/ band for MALDI-TOF, the sequence may be subjected to BLAST subsequently.