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Table 9 Example artifactual orphans

From: A survey of orphan enzyme activities

EC No.

Enzyme Name

Original Species


Swiss-Prot/TrEMBL Acc. No.

Cause of artifact

Significance of error; importance of orphan activity

Physarolisin (a proteinase)

Physarum flavicomum



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.

Maleimide hydrolase

Blastobacter sp. A17p-4



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.

Phthalyl amidase

Xanthobacter agilis



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.


Alteromonas sp.



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.