InterPro domain: IPR004305

Proteins containing this domain are found in all the three major phyla of life: archaebacteria, eubacteria, and eukaryotes. In Bacillus subtilis, TenA is one of a number of proteins that enhance the expression of extracellular enzymes, such as alkaline protease, neutral protease and levansucrase [ 1 ] and has been identified as a Thiaminase 2 [ 2 ]. The THI-4 protein, which is involved in thiamine biosynthesis, also contains this domain. The C-terminal part of these proteins consistently show significant sequence similarity to TenA proteins. This similarity was first noted with the Neurospora crassa THI-4 [ 3 ].

This domain is also found in bacterial coenzyme PQQ synthesis protein C or PQQC. Pyrroloquinoline quinone (PQQ) is the prosthetic group of several bacterial enzymes,including methanol dehydrogenase of methylotrophs and the glucose dehydrogenase of a number of bacteria [ 4 ]. PQQC has been found to be required in the synthesis of PQQ, but its function is unclear.

1. Cloning and characterization of a pair of novel genes that regulate production of extracellular enzymes in Bacillus subtilis. J. Bacteriol. 173, 46-54
2. Structural characterization of the regulatory proteins TenA and TenI from Bacillus subtilis and identification of TenA as a thiaminase II. Biochemistry 44, 2319-29
3. Molecular cloning of thi-4, a gene necessary for the biosynthesis of thiamine in Neurospora crassa. Curr. Genet. 30, 62-7
4. PqqC/D, which converts a biosynthetic intermediate to pyrroloquinoline quinone. Biochem. Biophys. Res. Commun. 299, 268-72