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Table 9 Example artifactual orphans

From: A survey of orphan enzyme activities

EC No. Enzyme Name Original Species Year Swiss-Prot/TrEMBL Acc. No. Cause of artifact Significance of error; importance of orphan activity
3.4.21.103 Physarolisin (a proteinase) Physarum flavicomum 1982 Q8MZS4 IUBMB entry lists a 2003 paper describing a gene coding for a protein with this activity [28]. Sequence is in Swiss-Prot but ENZYME does not reference this sequence. Lack of database cross-referencing presumably involving the long interval between the initial characterization of the activity and the cloning of the gene.
3.5.2.16 Maleimide hydrolase Blastobacter sp. A17p-4 1997 Q93T25 ENZYME and IUBMB entries are not referencing a Swiss-Prot entry from a 2002 paper describing the cloning of gene coding for this [29]. Lack of database cross-referencing is not restricted to older orphans.
3.5.1.79 Phthalyl amidase Xanthobacter agilis 1995 N/A The sequence, listed in a patent associated with a 1996 paper by [30] in Journal of Molecular Catalysis B: Enzymatic are available from Entrez, but not from TrEMBL. The paper itself is not available from PubMed. Note: though the protein sequence is not available from the UniProt database, the DNA sequence is present in the EMBL database.
3.1.8.2 Diisopropyl-fluoro-phosphatase Alteromonas sp. 1954 Q44238 ENZYME and IUBMB entries are not referencing a Swiss-Prot entry associated with a 1996 paper describing the cloning of a gene coding for an enzyme with this activity [31]. This enzymatic activity detoxifies nerve gas. The gene is part of a widespread gene family with otherwise unknown function, with members in Homo sapiens.